Should you update to Firefox 153?
No: install Firefox 159.0.1 instead. Firefox 153 is a security update Mozilla released on 21 Jul 2026 for Mac, Windows and Linux. It fixes 63 security flaws, 0 rated critical and 20 high by Mozilla.[1] None of them is known to be used in attacks.
It has since been replaced by Firefox 154, released 18 Aug 2026, which includes all of its fixes. If you’re on an older version, install that instead.
Should you update?
No: install Firefox 159.0.1 instead. Firefox 159.0.1 came out on 3 Nov 2026 and includes every fix in Firefox 153, so there’s no reason to stop at this one. Software Update offers the newest version your device can run.
Is Firefox 153 still safe?
Not any more. The 9 updates since, up to Firefox 159.0.1, fix 485 security flaws that Firefox 153 doesn’t, and each became public the day its fix shipped. Installing it is safe: get it only from Firefox’s own About window (☰ menu → Help → About Firefox), never from a link in an email, text or pop-up.
What it fixes
Mozilla lists 63 security flaws, 0 rated critical and 20 high by Mozilla.[1] The 20 critical and high ones are:
| Flaw | Severity | What Mozilla calls it |
|---|---|---|
CVE-2026-16349 | High | Same-origin policy bypass in the DOM: Navigation component |
CVE-2026-16350 | High | Incorrect boundary conditions in the Audio/Video: cubeb component |
CVE-2026-16362 | High | Use-after-free in the WebRTC: Audio/Video component |
CVE-2026-16351 | High | Sandbox escape due to use-after-free in the DOM: Navigation component |
CVE-2026-16352 | High | Sandbox escape due to use-after-free in the Disability Access APIs component |
CVE-2026-16363 | High | JIT miscompilation in the JavaScript: WebAssembly component |
CVE-2026-16364 | High | Incorrect boundary conditions in the Audio/Video: Playback component |
CVE-2026-16365 | High | Privilege escalation in the DOM: Workers component |
CVE-2026-16366 | High | Privilege escalation in the DOM: Navigation component |
CVE-2026-16353 | High | Invalid pointer in the DOM: Bindings (WebIDL) component |
CVE-2026-16354 | High | Information disclosure in the Graphics: ImageLib component |
CVE-2026-16367 | High | Sandbox escape due to invalid pointer in the Disability Access APIs component |
CVE-2026-16368 | High | Incorrect boundary conditions in the JavaScript: WebAssembly component |
CVE-2026-16369 | High | Integer overflow in the JavaScript: WebAssembly component |
CVE-2026-16355 | High | JIT miscompilation in the JavaScript Engine: JIT component |
CVE-2026-16356 | High | Sandbox escape due to use-after-free in the Disability Access APIs component |
CVE-2026-16357 | High | Incorrect boundary conditions in the Graphics component |
CVE-2026-16411 | High | Memory safety bugs fixed in Firefox 153 |
CVE-2026-16412 | High | Memory safety bugs fixed in Firefox ESR 140.13 and Firefox 153 |
CVE-2026-16360 | High | Memory safety bugs fixed in Firefox ESR 115.38, Firefox ESR 140.13 and Firefox 153 |
How to update, and how long it takes
A minute or two. Firefox restarts and reopens your tabs.
- Open Firefox’s About window.Open the ☰ menu → Help → About Firefox. Firefox checks for the update and downloads it.
- Click Restart to update Firefox.Firefox reopens your windows and tabs. Until it restarts, the old, unfixed version keeps running.
- Leave automatic updates on.In Settings → General → Firefox Updates, keep “Automatically install updates” selected.
To check it worked: The ☰ menu → Help → About Firefox shows the version. It should say 154 or later.
152.0.6 vs 153
Firefox 152.0.6, released 14 Jul 2026, fixed 2 security flaws. Firefox 153 fixes 63 security flaws and includes the fixes before it, so going straight to 153 gets you both.
- Before: Firefox 152.0.6, 14 Jul 2026, 2 security flaws
- After: Firefox 154, 18 Aug 2026, 58 security flaws
- Firefox updates, every release and the latest version
- Updates, the latest version of everything HARD tracks
References
- ^ Mozilla. “Security Vulnerabilities fixed in Firefox 153”, 21 Jul 2026.