Hi, Just noticed I have same thing. I guess did not notice as I have setup for Win10 so when hover it shows the windows more. Is this a add-on/Extension you were using ? Or CRTL+Tab ? A little more info please and will let someone else look at this. Thanks.

Hi,

It's actually odd because I have a second computer also running Windows 7 and Firefox 59 which doesn't have this problem.

Most of my addons got disabled after the update to Quantum, so I'm really not sure that it's anything to do with that. I've compared about:config settings regarding 'preview' and 'favicon' across both computers and even thought the settings for those options are the same, the issue still occurs on my main PC.

Hi, nice to know mine is broken also..... Is this something that is really important to you to get working again or would the hassle of uninstalls and refresh and backup Profile/bookmarks and back and forth messages worth the trouble if all else works fine.

Just trying to weigh your interest here :

Can try this 7min or so fix : Please uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 59.0 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

Please let us know if this solved your issue or if need further assistance.

Repair System Registry and Files Windows 7 Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN

Please type or copy & paste SFC /Scannow (SFC <space>/Scannow) into the Dos box then Enter This uses local files to fix issues, Win10 gets new files.

Reboot After

Please let us know if this solved your issue or if need further assistance.

Hi,

Thanks Pkshadow for your helpful suggestions. Unfortunately I've tried everything you asked and still can't resolve the issue.

Other things I tried:

Refreshing Firefox Renaming the Mozilla folder in AppData\Roaming\ Firefox in Safe Mode with addons disabled

It's really rather frustrating. Is there anything else you can suggest I do?

Cheers.

Hi, welcome, it may end up being something that never cures for awhile.

Can try this : Create a new profile as a TEST to check if your current profile is causing the problem.

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data
• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem. Never work with original files.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Can try this before the above : SAFE MODE

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

In Firefox Safe mode these changes are effective:

• all extensions are disabled (about:addons)
• default theme is used (no persona)
• userChrome.css and userContent.css are ignored (chrome folder)
• default toolbar layout is used (file: localstore-safe.rdf)
• Javascript JIT compilers are disabled (prefs: javascript.options.*jit)
• hardware acceleration is disabled (Options > Advanced > General)
• plugins are not affected
• preferences are not affected

TEST

Hey Pkshadow,

Thanks again, but I've already tried both of those in a somewhat roundabout way, and the issue is still occurring.

I've just discovered that the other system I was talking about that had no issues was only running Firefox 57.0.2. I have since updated Firefox to 59 and the problem is now happening on both systems. This is definitely a bug with the newest version.

I've also tried updating one system to Firefox 60.0b3, however the issue still persists in the latest beta.

How might this bug be reported to Mozilla to look at?

There is a bug on file:

Bug 1403620 - Options icon appears blank in "Show tab previews in the Windows taskbar" (Sept. 2017)

and another one

Bug 1433037 - taskbar preview's favicon appears blank (Jan. 2018)

Those are assigned priority P3, so they are not high on the "to do" list and may not get fixed in time for Firefox 60.

Notes on the bug tracking system:

• Bugzilla Etiquette
• Voting

I'm glad it's a filed bug and that it should hopefully get fixed in a later release. Makes me happier to feel that I'm not going crazy haha.