Which firefox version do you run? Can you try firefox-83.0 from latest updates?
Thanks.

Same issue here for firefox-83.0-3.fc33.x86_64 - nearly all extension menus are blank (e.g. uBlock Origin, Cookie AutoDelete, Violentmonkey).
For me, it only seems happen with the WebRender enabled firefox-wayland, firefox-x11 seems to work fine, so does firefox-wayland *without* WebRender enabled.

When spam clicking the extension menu button, it sometimes renders correctly.

firefox-82.0.3-2.fc33.x86_64 did work fine in all the above mentioned configurations.

Same here. Firefox 82.X works fine on Wayland with WebRender. Firefox 83 does not (unless you switch to X11 or disable WebRender)

(In reply to Martin Stransky from comment #1)
> Which firefox version do you run? Can you try firefox-83.0 from latest
> updates?
> Thanks.

firefox-83.0-3.fc33.x86_64
firefox-wayland-83.0-3.fc33.x86_64

Problem spotted in: 
 firefox-83.0-3.fc33.x86_64.rpm
 https://koji.fedoraproject.org/koji/buildinfo?buildID=1643127

 I don't see any newer (successful) builds in koji.

I've downgraded to: 
 firefox-82.0.3-1.fc33.x86_64

(In reply to John Fawkes from comment #2)
> Same issue here for firefox-83.0-3.fc33.x86_64 - nearly all extension menus
> are blank (e.g. uBlock Origin, Cookie AutoDelete, Violentmonkey).
> For me, it only seems happen with the WebRender enabled firefox-wayland,
> firefox-x11 seems to work fine, so does firefox-wayland *without* WebRender
> enabled.
> 
> When spam clicking the extension menu button, it sometimes renders correctly.
> 
> firefox-82.0.3-2.fc33.x86_64 did work fine in all the above mentioned
> configurations.

Thanks for the tip.  I stayed on wayland and disabled WebRender and extensions back to normal.

To be fair, WebRender under Linux hasn't been approved for default yet.  It appears they are
going to give it a try in Fx 84.  I had enabled in 82 and forgot about it.  

Probably should keep this open for those who forgot they had enabled WebRender.

Something happened between 82 and 83. WebRender was working fine on 82. There might be some regression in 83.

(In reply to Gerald Cox from comment #6)
> 
> Probably should keep this open for those who forgot they had enabled
> WebRender.

Just wanted to amend my comment... even with WebRender turned off, 
firefox-wayland is wonky on some sites.  I noticed when a website
popped open other windows to display a PDF that the window would flip
between transparent and solid when I moved my cursor over it.  It was
so bad shuttering back and forth I couldn't make out what was
in the window.  Bottom line, IMO firefox-wayland 83 is unusable.
You need to stick with the X11 version.

I encountered this bug on Firefox 83.0-3 and -8 and found a different workaround:

With WebRender still enabled, if I pin the extension button to the Overflow menu, and then invoke the extension from there, the extension's content is visible. 

Perhaps this is a clue to whomever is looking at this bug in the future.  I'll also comment on this upstream:
https://bugzilla.mozilla.org/show_bug.cgi?id=1679104

(In reply to Gerald Cox from comment #8)
> (In reply to Gerald Cox from comment #6)
> > 
> > Probably should keep this open for those who forgot they had enabled
> > WebRender.
> 
> Just wanted to amend my comment... even with WebRender turned off, 
> firefox-wayland is wonky on some sites.  I noticed when a website
> popped open other windows to display a PDF that the window would flip
> between transparent and solid when I moved my cursor over it.  It was
> so bad shuttering back and forth I couldn't make out what was
> in the window.  Bottom line, IMO firefox-wayland 83 is unusable.
> You need to stick with the X11 version.

Try installing egl-wayland and restart your browser. I had screen flickering without it because Firefox Wayland could not find this library.

(In reply to Robert-André Mauchin 🐧 from comment #10)
> (In reply to Gerald Cox from comment #8)
> > (In reply to Gerald Cox from comment #6)
> > > 
> > > Probably should keep this open for those who forgot they had enabled
> > > WebRender.
> > 
> > Just wanted to amend my comment... even with WebRender turned off, 
> > firefox-wayland is wonky on some sites.  I noticed when a website
> > popped open other windows to display a PDF that the window would flip
> > between transparent and solid when I moved my cursor over it.  It was
> > so bad shuttering back and forth I couldn't make out what was
> > in the window.  Bottom line, IMO firefox-wayland 83 is unusable.
> > You need to stick with the X11 version.
> 
> Try installing egl-wayland and restart your browser. I had screen flickering
> without it because Firefox Wayland could not find this library.

Thanks for the tip... that fixed the wayland flicker.  The question then is why
isn't egl-wayland a runtime requirement?

I did not experienced any flickering with webrender=true. Just the extension buttons were broken. 

I've installed egl-wayland and tested it again. It doesn't help with the extension problem. (but it should probably be a dependency for firefox)

(In reply to Milan Zink from comment #12)
> I did not experienced any flickering with webrender=true. Just the extension
> buttons were broken. 
> 
> I've installed egl-wayland and tested it again. It doesn't help with the
> extension problem. (but it should probably be a dependency for firefox)

Yeah, something happened with this upgrade.  The previous release didn't have this behavior.

In regards to the recommendation for egl-wayland mentioned in comment #10, that was
in response to my comment #8, which said that I was still receiving flickering with
webrender=false.

The actual upstream bug is https://bugzilla.mozilla.org/show_bug.cgi?id=1672139 which has been resolved, and is scheduled to be included in Firefox 84.

It wasn't uplifted to 83, so we have to wait I guess.

This update fixes it: https://bodhi.fedoraproject.org/updates/FEDORA-2020-ddb91506b1