- Debian Stable is currently on Firefox ESR 78.15 released 2021-10-05
- Version 91.x came out 2021-10-28 and has had 2 releases so far
Mozilla release calendar: https://wiki.mozilla.org/Release_Management/Calendar
According to this Mozilla doc, there’s “(at least 12 weeks) overlap between the time of a new release and the end-of-life of the previous release”
So while Mozilla won’t consider Debian’s ESR EOL until ~Jan 05, it’s a pretty major leap behind the current ESR.
There’s also this: “Maintenance of each ESR through point releases is limited to high-risk/high-impact security vulnerabilities” so lagging point releases is lagging behind high-risk/high-impact security vulnerabilities.