Firefox 159.0.1: passkey fixes, Windows crashes with security software, and MFSA2026-123
Mozilla released Firefox 159.0.1 on November 3, 2026, fixing passkey sign-in across related sites, Windows crashes with some security software, and a High-impact layout CVE.
Mozilla released Firefox 159.0.1 to the Release channel on November 3, 2026. The maintenance update fixes several desktop reliability issues and includes a security advisory rated High.
This is a follow-up to Firefox 159.0, not a new major feature train. TricknFix did not re-test every bug; the facts below come from Mozilla’s release notes and MFSA2026-123.
What Mozilla lists as fixed
The desktop release notes for 159.0.1 include:
- Passkeys across related sites — sign-in could fail on websites that share passkeys across related properties (Mozilla cites examples such as Facebook and Instagram).
- Windows crashes with some security software — crashes that could also leave WebGL disabled in some cases.
- Windows update restart — a command-prompt window briefly appearing when Firefox restarts to apply an update.
- Linux WebGL colours — red and blue appearing swapped on some WebGL sites, including video-call background effects.
- Tab attention indicator — the attention dot hard to see with some themes, depending on the system accent colour.
- Settings text wrapping — security-warning and similar descriptions breaking mid-word.
- Time-zone data — updated for Cuba’s decision not to end daylight saving time on November 1, 2026.
- Security fix — covered by MFSA2026-123.
Android 159.0.1 shares the passkey, time-zone and security items; the Windows command-prompt and Linux WebGL colour fixes are desktop-specific in the notes TricknFix consulted.
Security: MFSA2026-123
Mozilla Foundation Security Advisory 2026-123 (https://www.mozilla.org/en-US/security/advisories/mfsa2026-123/) is dated November 3, 2026, products Firefox, fixed in 159.0.1, overall impact high.
It documents CVE-2026-120572: incorrect boundary conditions in the Layout: Block and Inline component (Bug 2079035), impact high, reporter Mozilla.
This article does not claim active exploitation, a zero-day emergency beyond Mozilla’s wording, or that Chrome/Edge users are covered by the same advisory. Those browsers follow their own calendars (Chrome 157 Stable was covered separately on TricknFix).
How to check your version
On a personal PC:
- Open Firefox.
- Open the menu → Help → About Firefox (wording can vary by language).
- Let Firefox check for updates, then confirm the reported version is 159.0.1 or newer once the update reaches your device.
- Restart if Firefox asks you to.
On a work-managed PC, updates may arrive only through the organisation’s deployment tools. Checking “About” shows the installed version; it does not override IT policy.
Mozilla’s notes also remind readers that Firefox is no longer supported on Windows 8.1 and below, or on macOS 10.14 and below; those platforms should use Firefox ESR if they still need a Mozilla browser.
What this update does not establish
The 159.0.1 notes are a short maintenance list. They do not invent a full feature changelog for 159.0, do not prove every antivirus product is conflict-free after updating, and do not justify disabling antivirus, Secure Boot or site isolation as a “fix”. If passkey sign-in still fails after 159.0.1, keep the exact site, OS and Firefox version rather than treating this patch as a universal authentication repair.
Sources
- Firefox 159.0.1 Release Notes (https://www.firefox.com/en-US/firefox/159.0.1/releasenotes/) — November 3, 2026 desktop fix list.
- MFSA2026-123: Security vulnerabilities fixed in Firefox 159.0.1 (https://www.mozilla.org/en-US/security/advisories/mfsa2026-123/) — High impact; CVE-2026-120572.
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