Hi Carlos,

Please try running Firefox in Troubleshoot Mode. Does the problem persist? If not, please follow the steps from this article to troubleshoot further.

Looking forward to your update!

Very impressive, you gave me a very quick response and after just a couple of clicks on your Troubleshoot Mode and my sidebar issue was solved. I hope that no other issues have cropped up now. :-) Thank you very much for your help, you have saved me hours and hours of aggravation.

While in Troubleshoot mode my sidebar returned to normal but this disabled most of my other settings. When I exited the Troubleshooting mode the dark sidebar issue returned. How do I trouble shoot the setting that is causing the dark sidebar issue?

If not, please follow the steps from this article to troubleshoot further.

If the problem doesn't occur in Troubleshoot Mode, the likely cause is an extension, theme or hardware acceleration. See the mentioned article for troubleshooting steps.

Very, very interesting. One of the color themes that I have used for years had caused the conflict with the side bar and after I switched to a different color theme the sidebar problem went away. I tried switching back to my old theme and the problem was still there. How very odd that my theme of many years all of a sudden gave up the ghost. Your link to the step by step troubleshooting process was very helpful. I really appreciate you sticking with me to help me get this issue resolved. Something that Firefox did in the last 24 hours caused this issue and I just don't understand why. I guess that it is unhappy with me for not donating more each year. LOL Thank you again. Have some very Happy Holidays. P.S. I hope that I don't need your help anymore any time soon. :-)

Carlos,

Is it a default theme? If not, you should be able to find it on addons.mozilla.org and report the issue to the developer (look for Support site / Homepage). There were some changes around light/dark theme coloring in the latest update, and I assume they may require themes to get updated in order to keep working normally.