Test the new Content Security Policy for Content Scripts

Firefox

As part of our efforts to make add-ons safer for users, and to support evolving manifest v3 features, we are making changes to apply the Content Security Policy (CSP) to content scripts used in extensions. These changes will make it easier to enforce our long-standing policy of disallowing execution of remote code.

When this feature is completed and enabled, remotely hosted code will not run, and attempts to run them will result in a network error. We have taken our time implementing this change to decrease the likelihood of breaking extensions and to maintain compatibility. Programmatically limiting the execution of remotely hosted code is an important aspect of manifest v3, and we feel it is a good time to move forward with these changes now.

We have landed a new content script CSP, the first part of these changes, behind preferences in Firefox 72. We’d love for developers to test it out to see how their extensions will be affected.

Testing instructions

Using a test profile in Firefox Beta or Nightly, please change the following preferences in about:config:

  • Set extensions.content_script_csp.enabled to true
  • Set extensions.content_script_csp.report_only to false to enable policy enforcement

This will apply the default CSP to the content scripts of all installed extensions in the profile.

Then, update your extension’s manifest to change your content_security_policy. With the new content script CSP,  content_scripts works the same as extension_pages. This means that the original CSP value moves under the extension_pages key and the new content_scripts key will control content scripts.

Your CSP will change from something that looks like:

content_security_policy: "script-src 'self'; object-src 'none'"

To something that looks like:

content_security_policy: {
  extension_pages: "script-src 'self'; object-src 'none'",
  content_scripts: "script-src 'self'; object-src 'none'"
}

Next, load your extension in about:debugging. The default CSP now applied to your content scripts will prevent the loading of remote resources, much like what happens when you try to  insert an image into a website over http, possibly causing your extension to fail. Similar to the old content_security_policy (as documented on MDN), you may make changes using the content_scripts key.

Please do not loosen the CSP to allow remote code, as we are working on upcoming changes to disallow remote scripts.

As a note, we don’t currently support any other keys in the content_security_policy object. We plan to be as compatible as possible with Chrome in this area will support the same key name they use for content_scripts in the future.

Please tell us about your testing experience on our community forums. If you think you’ve found a bug, please let us know on Bugzilla.

Implementation timeline

More changes to the CSP for extensions are expected to land behind preferences in the upcoming weeks. We will publish testing instructions once those updates are ready. The full set of changes should be finished and enabled by default in 2020, meaning that you will be able to use the new format without toggling any preferences in Firefox.

Even after the new CSP is turned on by default, extensions using manifest v2 will be able to continue using the string form of the CSP. The object format will only be required for extensions that use manifest v3 (which is not yet supported in Firefox).

There will be a transition period when Firefox supports both manifest v2 and manifest v3 so that developers have time to update their extensions. Stay tuned for updates about timing!

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Secure your addons.mozilla.org account with two-factor authentication

Firefox

Accounts on addons.mozilla.org (AMO) are integrated with Firefox Accounts, which lets you manage multiple Mozilla services from one login. To prevent unauthorized people from accessing your account, even if they obtain your password, we strongly recommend that you enable two-factor authentication (2FA). 2FA adds an extra layer of security to your account by adding an additional step to the login process to prove you are who you say you are.

When logging in with 2FA enabled, you will be asked to provide a verification code from an authentication application, in addition to your user name and password. This article on support.mozilla.org includes a list of supported authenticator applications.

Starting in early 2020, extension developers will be required to have 2FA enabled on AMO. This is intended to help prevent malicious actors from taking control of legitimate add-ons and their users. 2FA will not be required for submissions that use AMO’s upload API.

Before this requirement goes into effect, we’ll be working closely with the Firefox Accounts team to make sure the 2FA setup and login experience on AMO is as smooth as possible. Once this requirement goes into effect, developers will be prompted to enable 2FA when making changes to their add-ons.

You can enable 2FA for your account before the requirement goes into effect by following these instructions from support.mozilla.org.

Once you’ve finished the set-up process, be sure to download or print your recovery codes and keep them in a safe place. If you ever lose access to your 2FA devices and get locked out of your account, you will need to provide one of your recovery codes to regain access. Misplacing these codes can lead to permanent loss of access to your account and your extensions on AMO.

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2019 Add-ons Community Meetup in London

Firefox

At the end of October, the Firefox add-ons team hosted a day-long meetup with a group of privacy extension developers as part of the Mozilla Festival in London, UK. With 2019 drawing to a close, this meetup provided an excellent opportunity to hear feedback from developers involved in the Recommended Extensions program and to get input about some of our plans for 2020.

Recommended Extensions

Earlier this summer we launched the Recommended Extensions program to provide Firefox users with a list of curated extensions that meet the highest standards of security, utility, and user experience. Participating developers agree to actively maintain their extensions and to have each new version undergo a code review. We invited a handful of Recommended developers to attend the meetup and gather their feedback about the program so far. We also discussed more general issues around publishing content on addons.mozilla.org (AMO), such as ways of addressing user concerns over permission prompts.

Scott DeVaney, Senior Editorial & Campaign Manager for AMO, led a session on ways developers can improve a few key experiential components of their extensions. These tips may be helpful to the developer community at large:

  • AMO listing page. Use clear, descriptive language to convey exactly what your extension does and how it benefits users. Try to avoid overly technical jargon that average users might not understand. Also, screenshots are critical. Be sure to always include updated, relevant screenshots that really capture your extension’s experience.
  • Extension startup/post-install experience. First impressions are really important. Developers are encouraged to take great care in how they introduce new users to their extension experience. Is it clear how users are supposed to engage with the content? Or are they left to figure out a bunch of things on their own with little or no guidance? Conversely, is the guidance too cumbersome (i.e. way too much text for a user to comfortably process?)
  • User interface. If your extension involves customization options or otherwise requires active user engagement, be sure your settings management is intuitive and all UI controls are obvious.

Monetization. It is of course entirely fine for developers to solicit donations for their work or possibly even charge for a paid service. However, monetary solicitation should be tastefully appropriate. For instance, some extensions solicit donations just after installation, which makes little sense given the extension hasn’t proven any value to the user yet. We encourage developers to think through their user experience to find the most compelling moments to ask for donations or attempt to convert users to a paid tier.

WebExtensions API and Manifest v3

One of our goals for this meetup was to learn more about how Firefox extension developers will be affected by Chrome’s proposed changes to their extensions API (commonly referred to as Manifest v3).  As mentioned in our FAQ about Manifest v3, Mozilla plans to adopt some of these changes to maintain compatibility for developers and users, but will diverge from Chrome where it makes sense.

Much of the discussion centered around the impact of changes to the `blocking webRequest` API and replacing background scripts with service workers. Attendees outlined scenarios where changes in those areas will cause breakage to their extensions, and the group spent some time exploring possible alternative approaches for Firefox to take. Overall, attendees agreed that Chrome’s proposed changes to host permission requests could give users more say over when extensions can run. We also discussed ideas on how the WebExtensions API could be improved in light of the goals Manifest v3 is pursuing.

More information about changes to the WebExtensions API for Manifest v3 compatibility will be available in early 2020. Many thanks to everyone who has contributed to this conversation over the last few months on our forums, mailing list, and blogs!

Firefox for Android

We recently announced that Firefox Preview, Mozilla’s next generation browser for Android built on GeckoView, will support extensions through the WebExtensions API. Members of the Android engineering team will build select APIs needed to initially support a small set of Recommended Extensions.

The group discussed a wishlist of features for extensions on Android, including support for page actions and browser actions, history search, and the ability to manipulate context menus. These suggestions will be considered as work on Firefox Preview moves forward.

Thank you

Many thanks to the developers who joined us for the meetup. It was truly a pleasure to meet you in person and to hear first hand about your experiences.

The add-ons team would also like to thank Mandy Chan for making us feel at home in Mozilla’s London office and all of her wonderful support during the meetup.

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Extensions in Firefox 71

Firefox

Firefox 71 is a light release in terms of extension changes. I’d like to tell you about a few interesting improvements nevertheless.

Thanks to Nils Maier, there have been various improvements to the downloads API, specifically in handling download failures. In addition to previously reported failures, the browser.downloads.download API will now report an error in case of various 4xx error codes. Similarly, HTTP 204 (No Content) and HTTP 205 (Reset Content) are now treated as bad content errors. This makes the API more compatible with Chrome and gives developers a way to handle these errors in their code. With the new allowHttpErrors parameter, extensions may also ignore some http errors when downloading. This will allow them to download the contents of server error pages.

Please also note, the lowercase isarticle filter for the tabs.onUpdated listener has been removed in Firefox 71. Developers should instead use the camelCase isArticle filter.

A few more minor updates are available as well:

  • Popup windows now include the extension name instead of its moz-extension:// url when using the windows.create API.
  • Clearer messaging when encountering unexpected values in manifest.json (they are often warnings, not errors)
  • Extension-registered devtools panels now interact better with screen readers

Thank you contributors Nils and Myeongjun Go for the improvements, as well as our WebExtensions team for fixing various tests and backend related issues. If you’d like to help make this list longer for the next releases, please take a look at our wiki on how to contribute. I’m looking forward to seeing what Firefox 72 will bring!

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Security improvements in AMO upload tools

Firefox

We are making some changes to the submission flow for all add-ons (both AMO- and self-hosted) to improve our ability to detect malicious activity.

These changes, which will go into effect later this month, will introduce a small delay in automatic approval for all submissions. The delay can be as short as a few minutes, but may take longer depending on the add-on file.

If you use a version of web-ext older than 3.2.1, or a custom script that connects to AMO’s upload API, this new delay in automatic approval will likely cause a timeout error. This does not mean your upload failed; the submission will still go through and be approved shortly after the timeout notification. Your experience using these tools should remain the same otherwise.

You can prevent the timeout error from being triggered by updating web-ext or your custom scripts before this change goes live. We recommend making these updates this week.

  • For web-ext: update to web-ext version 3.2.1, which has a longer default timeout for `web-ext sign`. To update your global install, use the command `npm install -g web-ext`.
  • For custom scripts that use the AMO upload API: make sure your upload scripts account for potentially longer delays before the signed file is available. We recommend allowing up to 15 minutes.

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Firefox to discontinue sideloaded extensions

Firefox

Sideloading is a method of installing an extension in Firefox by adding an extension file to a special location using an executable application installer. This installs the extension in all Firefox instances on a computer.

Sideloaded extensions frequently cause issues for users since they did not explicitly choose to install them and are unable to remove them from the Add-ons Manager. This mechanism has also been employed in the past to install malware into Firefox. To give users more control over their extensions, support for sideloaded extensions will be discontinued. 

During the release cycle for Firefox version 73, which goes into pre-release channels on December 3, 2019 and into release on February 11, 2020, Firefox will continue to read sideloaded files, but they will be copied over to the user’s individual profile and installed as regular add-ons. Sideloading will stop being supported in Firefox version 74, which will be released on March 10, 2020. The transitional stage in Firefox 73 will ensure that no installed add-ons will be lost, and end users will gain the ability to remove them if they chose to.

If you self-distribute your extension via sideloading, please update your install flows and direct your users to download your extension through a web property that you own, or through addons.mozilla.org (AMO). Please note that all extensions must meet the requirements outlined in our Add-on Policies and Developer Agreement.  If you choose to continue self-distributing your extension, make sure that new versions use an update URL to keep users up-to-date. Instructions for distributing an extension can be found in our Extension Workshop document repository.

If you have any questions, please head to our community forum.

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Firefox Preview/GeckoView Add-ons Support

Firefox

Back in June, Mozilla announced Firefox Preview, an early version of the new browser for Android that is built on top of Firefox’s own mobile browser engine, GeckoView. We’ve gotten great feedback about the superior performance of GeckoView so far. Not only is it faster than ever, it also opens up many opportunities for building deeper privacy features that we have already started exploring, and a lot of users were wondering what this step meant for add-ons.

We’re happy to confirm that GeckoView is currently building support for extensions through the WebExtensions API. This feature will be available in Firefox Preview, and we are looking forward to offering a great experience for both mobile users and developers.

Bringing GeckoView and Firefox Preview up to par with the APIs that were supported previously in Firefox for Android won’t happen overnight. For the remainder of 2019 and leading into 2020, we are focusing on building support for a selection of content from our Recommended Extensions program that work well on mobile and cover a variety of utilities and features.

At the moment, Firefox Preview does not yet officially support extensions. While some members of the community have discovered that some extensions inadvertently work in Firefox Preview, we do not recommend attempting to install them until they are officially supported as other issues may arise. We expect to implement support for the initial selection of extensions in the first half of 2020, and will post updates here as we make progress.

If you haven’t yet had a chance, why don’t you give Firefox Preview a try and let us know what you think.

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Search Engine add-ons to be removed from addons.mozilla.org

Firefox

For the last eleven years, Firefox Search Engine add-ons have been powered by OpenSearch. With the recent implementation of the search overrides API, a WebExtensions API that offers users more controls for opting into changes, Mozilla intends to deprecate OpenSearch and eventually remove it from Firefox. Search Engine add-ons will be removed from AMO on December 5, 2019.

For Search Engine add-ons to continue working, they must be converted to an extension using the WebExtensions API by December 3, 2019. For more information, please see the following documents on MDN web docs:

Unfortunately, it is not possible to automatically migrate users of Search Engine add-ons to their replacement extensions. If you are the developer of a Search Engine add-on, we recommend linking to your new extension’s listing page from your search add-on’s listing page so your users know where to install the update.

If you have any questions, please ask them in our community forum.

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Extensions in Firefox 70

Firefox

Welcome to another round of new additions and changes to extensions, this time in Firefox 70. We have a new API, some improvements on existing APIs, and some great additions to Firefox Developer Tools to make it easier to debug your extensions.

Network Status

Firefox 70 features a new network status API. It can be used to determine if an internet connection is available and provides insight into what type of connection the user is on. A potential use case for this would be for developers to limit the data they are transferring on a mobile connection. Here is an example:

async function upload(url, buffer) {
let info = await browser.networkStatus.getLinkInfo();
let isMobile = ["wimax", "2g", "3g", "4g"].includes(info.type);
// Only sending every second byte on mobile. Clever savings, eh?
let body = buffer;
if (isMobile) {
body = body.filter((elem, index) => index % 2 == 0);
}
console.log(`Uploading via ${info.type} connection named ${info.id}`);
switch (info.status) {
case "down":
await handleOfflineMode(url, buffer);
break;
case "up":
case "unknown":
await fetch(url, {
method: "POST",
headers: { "Content-Type": "application/octet-stream" },
body: body
});
break;
}
}

There is also an onConnectionChanged event available that is called with the changed link info.

Downloads API Improvements

We’ve made a few improvements to the downloads API in Firefox 70. By popular request, the Referer header is now allowed in the browser.downloads.download API’s headers object. This allows extensions, such as download managers, to download files for sites that require a referrer to be set.

Also, we’ve improved error reporting for failed downloads. In addition to previously reported failures, the browser.downloads.download API will now report an error in case of various http 4xx failures. This makes the API more compatible with Chrome and gives developers a way to react to these errors in their code. [Edit: Sorry if I got your hopes up! This is actually coming in Firefox 71!]

Privacy API Improvements

If you are using the browser.privacy.network API and are modifying webRTCIPHandlingPolicy, we’ve made some compatibility changes to the disable_non_proxied_udp setting. This setting now better matches Chrome’s behavior. If your add-on relied on the Firefox-specific behavior, you can make use of the new setting proxy_only.

Extension Storage Inspector

Starting in Firefox 70, Firefox finally supports inspecting data from the browser.storage API using the Devtools Storage Inspector. When you inspect an add-on via about:debugging, you will find a new Extension Storage section in the storage panel. While changing the values is not currently supported, this will make debugging your add-ons even easier.

Firefox developer tools showing extension storage data in a multi-column list.

Extension Storage Inspector

Unsupported Theme Properties

The accentcolor, headerURL and text_color properties are now unsupported. Please make use of the replacement properties frame, theme_frame, and tab_background_text. You can find more information on our previous deprecation announcement.

Miscellaneous

  • When managing extension shortcuts, you will now be notified if a shortcut is already in use.
  • The browser.notifications.onClicked and browser.notifications.onShown event callbacks are no longer called with a superfluous second parameter.
  • Logging has been improved when the native messaging host manifest is missing.
  • Various performance improvements, making startup quicker for Firefox users with add-ons.

Special thanks this time goes to our volunteers Trishul Goel, Myeongjun Go, Graham McKnight and Tom Schuster. We’ve also received an awesome contribution from Mandy Cheang as part of her internship at Mozilla. Keep up the great work everyone!

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Mozilla’s Manifest v3 FAQ

Firefox

What is Manifest v3?

Chrome versions the APIs they provide to extensions, and the current format is version 2. The Firefox WebExtensions API is nearly 100% compatible with version 2, allowing extension developers to easily target both browsers.

In November 2018, Google proposed an update to their API, which they called Manifest v3. This update includes a number of changes that are not backwards-compatible and will require extension developers to take action to remain compatible.

A number of extension developers have reached out to ask how Mozilla plans to respond to the changes proposed in v3. Following are answers to some of the frequently asked questions.

Why do these changes negatively affect content blocking extensions?

One of the proposed changes in v3 is to deprecate a very powerful API called blocking webRequest. This API gives extensions the ability to intercept all inbound and outbound traffic from the browser, and then block, redirect or modify that traffic.

In its place, Google has proposed an API called declarativeNetRequest. This API impacts the capabilities of content blocking extensions by limiting the number of rules, as well as available filters and actions. These limitations negatively impact content blockers because modern content blockers are very sophisticated and employ layers of algorithms to not only detect and block ads, but to hide from the ad networks themselves. Extensions would still be able to use webRequest but only to observe requests, not to modify or block them.

As a result, some content blocking extension developers have stated they can no longer maintain their add-on if Google decides to follow through with their plans. Those who do continue development may not be able to provide the same level of capability for their users.

Will Mozilla follow Google with these changes?

In the absence of a true standard for browser extensions, maintaining compatibility with Chrome is important for Firefox developers and users. Firefox is not, however, obligated to implement every part of v3, and our WebExtensions API already departs in several areas under v2 where we think it makes sense.

Content blocking: We have no immediate plans to remove blocking webRequest and are working with add-on developers to gain a better understanding of how they use the APIs in question to help determine how to best support them.

Background service workers: Manifest v3 proposes the implementation of service workers for background processes to improve performance. We are currently investigating the impact of this change, what it would mean for developers, and whether there is a benefit in continuing to maintain background pages.

Runtime host permissions: We are evaluating the proposal in Manifest v3 to give users more granular control over the sites they give permissions to, and investigating ways to do so without too much interruption and confusion.

Cross-origin communication: In Manifest v3, content scripts will have the same permissions as the page they are injected in. We are planning to implement this change.

Remotely hosted code: Firefox already does not allow remote code as a policy. Manifest v3 includes a proposal for additional technical enforcement measures, which we are currently evaluating and intend to also enforce.

Will my extensions continue to work in Manifest v3?

Google’s proposed changes, such as the use of service workers in the background process, are not backwards-compatible. Developers will have to adapt their add-ons to accommodate these changes.

That said, the changes Google has proposed are not yet stabilized. Therefore, it is too early to provide specific guidance on what to change and how to do so. Mozilla is waiting for more clarity and has begun investigating the effort needed to adapt.

We will provide ongoing updates about changes necessary on the add-ons blog.

What is the timeline for these changes?

Given Manifest v3 is still in the draft and design phase, it is too early to provide a specific timeline. We are currently investigating what level of effort is required to make the changes Google is proposing, and identifying where we may depart from their plans.

Later this year we will begin experimenting with the changes we feel have a high chance of being part of the final version of Manifest v3, and that we think make sense for our users. Early adopters will have a chance to test our changes in the Firefox Nightly and Beta channels.

Once Google has finalized their v3 changes and Firefox has implemented the parts that make sense for our developers and users, we will provide ample time and documentation for extension developers to adapt. We do not intend to deprecate the v2 API before we are certain that developers have a viable path forward to migrate to v3.

Keep your eyes on the add-ons blog for updates regarding Manifest v3 and some of the other work our team is up to. We welcome your feedback on our community forum.

 

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