Except where noted, everything here applies to both Firefox 92 and the Firefox 91.1 ESR.
- Extensions installed from the local file system became reenabled in some cases. This was fixed in bug 1715965.
- Firefox 78 ESR is the last version of Firefox that supports Flash. The last version of that ESR will be 78.15, which is scheduled to be released on 2021-10-05. This means that Flash will officially be out of support on Firefox when Firefox 78 ESR reaches EOL on 2021-11-02.
- Firefox 78 ESR is the last version of Firefox that supports macOS versions < 10.12.