While most Firefox users probably don’t need the functionality, some may have used it for certain useful operations such as killing sticky elements on a page, changing the referrer on the fly or edit any website you come across temporarily.
The Firefox 63 changelog does not mention the change; considering that Mozilla makes hundreds of changes to Firefox, it is clear that it represents only a small portion of changes.
Thankfully, it is possible to undo the change by changing the value of a preference of the web browser. Here is how that is done:
- You may get a warning page. Accept the warning to continue.
You can undo the change at any time by repeating the three steps outlined above.