One more item to note. It appears that the tabs are being treated as if they are the titlebar of the browser. Changing to different themes has not worked to resolve this issue.

Uninstall/delete Firefox Program Files where ever they maybe except your Profile Folder

Compile / Reinstall with Current Release Firefox 57.0.2 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.

PKShadow, uninstalling and removing all mozilla and firefox directories in /usr and installing the latest Firefox Quantum appears to have worked. Looking at the add-ons, it's clear that something is different in the chrome/skin (?) so I suspect the issue is the RPM packages that comes from the Fedora repository. I'm just surprised that more people using Fedora aren't experiencing it. It's possible that it's specific to Korora, but my understanding is that they package Fedora with RPMFusion and change branding to Korora.

Screenshots of the new add-ons screen from Firefox Quantum for comparison with the add-ons screens I posted yesterday are attached. Thanks for the help and please let me know if I should post anything else to dig further into the issue.

BTW, the package that was included with Korora that I removed was:

firefox-57.0-2.fc25.x86_64

eno2001

Linux distros are typically "spun" from source code and have contained minor differences vs the Mozilla builds for Linux. For many years some "spins" from source code changed so much in Firefox that Mozilla objected to them being being named "Firefox"; although most of those were for Windows operating systems, but not exclusively. Within that last year or so, Mozilla has been more accepting of "aftermarket" builds that modify certain features and preferences, and now allow them to be named Firefox, for Linux OS's.

Try to toggle this pref on the about:config page.

• browser.tabs.drawInTitlebar

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• http://kb.mozillazine.org/about:config

cor-el, oddly enough, when I tried reinstalling firefox with the 'dnf' command, it pulled a different version from the Fedora repository:

firefox-57.0.1-1.fc25.x86_64

Based on their versioning, this would appear to be a step back one version with a patch to make it 57.0.1-1. Running this version removes the problem, and also appears to remove their hidden custom chrome/skin as it now looks no different from the binary I downloaded from mozilla.org the other day.

I'm not sure if I should have just uninstalled and re-installed, because running 'dnf update' never changed the previous firefox-57.0-2.fc25.x86_64 version of the browser.

As a side note, I put the binary I downloaded into /usr/local/firefox as a temporary location. It isn't in my path and the libraries should not be accessible to the distro's version of FF. One thing I haven't done but will try when I get time is to start with a clean profile to see if running the official release from Mozilla has modified my profile in a way that resolves the issue with the distro version.

Trying with a new ~/.mozilla profile did not change anything. The problem is gone in the FF included with Fedora 25. Perhaps they backed it off a version if others experienced the same issue and either resolved it a day or two after I removed mine, or the 'dnf' command wouldn't downgrade it without additional command line options. Either way, my problem is now resolved and it looks like it had to do with the Fedora chrome/skin customization that originally applied to FF which does not appear to be there now.