Last checked · Check before installing; only use the official link.
Today: 2 listed problems, all with a fix. Update and you're fine.
Last checked . A popular privacy-focused web browser.
The minimum safe version
There is no single version number for Firefox. The newest fix listed here is: 159.0.1 (ESR: 153.6 or 115.44). If you have that or anything newer, you're covered against the fixed problems listed here (see the notes below).
- Only partly fixed so far, so also follow the extra steps on their pages: Fake website certificates: browsers and computers are blocking a certificate company's weak keys.
- These are fixed by an update without one version number we can compare, so check their pages: Fake website certificates: browsers and computers are blocking a certificate company's weak keys, Firefox 159 fixes 167 security bugs, and 159.0.1 fixes one more.
Where this number comes from:
- Mozilla: Security fixes in Firefox 159 (MFSA 2026-118) (Oct 27, 2026)
- Mozilla: Security fix in Firefox 159.0.1 (MFSA 2026-123) (Nov 3, 2026)
- Mozilla: Security fixes in Firefox ESR 115.44 (MFSA 2026-119) (Oct 27, 2026)
- Mozilla: Security fixes in Firefox ESR 153.6 (MFSA 2026-120) (Oct 27, 2026)
How to check your version
These steps only look. They do not change anything.
On Windows
Easy way: Click the three lines at the top right > Help > About Firefox. Firefox checks for updates there.
Or type this in PowerShellRead-only. It only reads the version and changes nothing.
Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*','HKLM:\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall\*','HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*' -ErrorAction SilentlyContinue | Where-Object DisplayName -like '*Mozilla Firefox*' | Select-Object DisplayName,DisplayVersion
On Mac
Easy way: Firefox menu bar: Firefox > About Firefox.
Or type this in TerminalRead-only. It only reads the version and changes nothing.
defaults read "/Applications/Firefox.app/Contents/Info" CFBundleShortVersionString
On Linux
Easy way: Firefox menu > Help > About Firefox.
Or type this in TerminalRead-only. It only reads the version and changes nothing.
firefox --version
How to update Firefox
Firefox updates itself. Open Help > About Firefox to start it now, then click Restart.
On Windows
- Open the menu > Help > About Firefox.
- Wait while it downloads the update.
- Click Restart to update Firefox.
On Mac
- Open the menu > Help > About Firefox.
- Wait while it downloads the update.
- Click Restart to update Firefox.
On Linux
- Open the menu > Help > About Firefox.
- Wait while it downloads the update.
- Click Restart to update Firefox.
Official update page Official website
Check before installing, and only use the official link. Never install an "update" from a pop-up, email or ad.
Latest problems (2)
- Firefox 159 fixes 167 security bugs, and 159.0.1 fixes one more Patched: update now updated Nov 3, 2026
- Fake website certificates: browsers and computers are blocking a certificate company's weak keys Partly patched updated Oct 27, 2026
For AI agents
This app as data, with minimum_safe_version: /products/firefox.json. What changed lately: /changes.json. Read-only checks only; ask before installing anything.