Block Widget Editor: Unable to edit the legacy text widget block in Firefox

[arinoch]

Users of Firefox version 91 are unable to edit the legacy text widget in block widget mode. They are required to install the classic widget plugin in order to make any changes.

Additional Note: Legacy text widget is not available by default in the block editor. I needed to switch to classic widgets to add it in my testing.

Steps to reproduce

1: If not already installed before the conversion to block widgets, you will need the classic widgets plugin. Install it, then Appearance > Customizer > Widgets > Add Widget, and add the text widget. 2: If you installed the classic Widgets plugin in step 1, deactivate or remove it. 3: In Firefox, navigate to Appearance > Customizer > Widgets, find where you've added your text widget, click to edit it. 4: Attempt to edit the text you configured there (if any) when you installed it, or add new text if not.

What I expected

It should allow you to edit the text widget as per normal without issue.

What happened instead

It returns you to the list of widgets you've added, as though you hadn't opted to add the text widget.

Reported by: Business plan WordPress.com user in: 31082825-hc Tested by: Me, internally, using a WordPress.com Business plan and the Twenty Twenty-One theme as well as a WordPress.com personal plan using the Hever theme.

I have verified this works in latest Chrome, but not Latest Firefox. Reporting user was on Windows 10, as was my testing.

[arinoch]

Additional testing: This appears to also be present in self-hosted WordPress.

[dpasque]

Tagging @Automattic/flow-patrol-create based on issue content

[cuemarie]

Possible report here: 4237863-zd-woothemes Have asked for confirmation and browser information. In troubleshooting their issues with editing existing Legacy Text widgets, I was unable to edit the Text widgets when SU'd, using Firefox.

Workarounds: Could edit in Text view, but not Visual view inside legacy widget.