Affected versions

• 76.0, 77.0a1; 75.0;

Affected platforms

• macOS 10.15.3, Ubuntu 18, Windows 10;

Steps to reproduce

1. Launch Firefox, access about:preferences
2. Navigate between the subsection (general/home/search/security/updates);
3. Click on the General subsection (about:preferences#general)
4. Scroll to Fonts and click to open the Advanced modal;
5. Click on the Back button to navigate to previous page

Expected result

• modal should close even if navigating to another subpage;

Actual result

• navigation is unhindered but modal remains displayed;

Regression range

• bit tricky since considering old behaviours had to take as good builds that when pressing back did close the menu but did not navigate to the previous subpage;
• First bad: 2017-06-05;
• Last good: 2017-06-04;
• Pushlog: URL
• Potential regressor:

Additional notes

• attached recording with the issue.

Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is P3 (Backlog,) indicating it has been triaged, the bug's Severity is being updated to S3 (normal.)