I updated from 126.96.36.199 to 3.4.x (whatever is the latest a couple days ago, I think 2.4.0). The software is now pulling the localhost/favicon instead of the favicon defined by the link element. Showing individual frames works fine however phpMyAdmin works better with frames for me. I used WinMerge to see if there was any difference between 3.2 and 3.4 and there wasn't. I'm not sure how this regressed. There is a known Firefox bug that I don't think was ever resolved (https://bugzilla.mozilla.org/show_bug.cgi?id=261912). unfortunately I have never encountered this before and I don't see any straight forward answer to resolving this regression. I also tried retaining the original icon just to be sure. I'm not sure else what I could try other then continuing to use version 3.2.
This bug is important to me as I quickly identify tabs based off of their favicon. I highly prefer phpMyAdmin's favicon over my own so I can quickly locate the tab where the software is open as I use it frequently. I now have to use the older 3.2.x version in order to maintain my normal work environment.