Firefox ESR updates
The latest version of Firefox ESR is 153.6, which Mozilla released on 27 Oct 2026. It fixes 145 security flaws.[1] It fixes 145 security flaws, and attackers study each release to work out what it fixed.
Since June 2026, Mozilla has put out 22 Firefox ESR security releases.
Should you update your browser?
Yes, this week. Firefox ESR 153.6 came out on 27 Oct 2026. None of its 145 fixes is known to be used in attacks yet. Its page lists what each fix covers. Not ready for Firefox ESR 153, or on a device that can’t run it? Firefox ESR 115.44 has the fixes for Firefox ESR 115.
Older devices
Mozilla keeps fixing older versions for devices that can’t run the newest one. The newest release on each:
| Version | Released | Fixes |
|---|---|---|
| Firefox ESR 153.6 | 145 | |
| Firefox ESR 115.44 | 80 | |
| Firefox ESR 140.17 | 43 |
How to update
- Open Firefox’s About window.Open the ☰ menu → Help → About Firefox. If your workplace or school manages Firefox, its IT team may install ESR updates for you.
- Click Restart to update Firefox.Firefox reopens your windows and tabs. Until it restarts, the old, unfixed version keeps running.
To see which version you have: The ☰ menu → Help → About Firefox shows the version, ending in esr.
Every release
Every Firefox ESR security release since June 2026, newest first.
References
- ^ Mozilla. “Mozilla Foundation Security Advisories”, each release’s notes.