Should you update to Firefox 151.0.3?

From Firefox updates, in the HARD wiki · Updated 2 Jun 2026

This article is about one Firefox release. For the latest version, see Firefox updates.

Firefox 151.0.3

Made by	Mozilla
For	Mac, Windows and Linux
Released	2 Jun 2026
Security fixes	2
Critical, high	0, 2
Used in attacks	None known
Install	No: Firefox 159.0.1 instead
Status	Replaced by Firefox 152
Source	Mozilla’s release notes

No: install Firefox 159.0.1 instead. Firefox 151.0.3 is a security update Mozilla released on 2 Jun 2026 for Mac, Windows and Linux. It fixes 2 security flaws, 0 rated critical and 2 high by Mozilla.^[1] None of them is known to be used in attacks.

It has since been replaced by Firefox 152, released 16 Jun 2026, which includes all of its fixes.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 151.0.3, so there’s no reason to stop at this one. Software Update offers the newest version your device can run.

Is Firefox 151.0.3 still safe?

Not any more. The 13 updates since, up to Firefox 159.0.1, fix 591 security flaws that Firefox 151.0.3 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 2 security flaws, 0 rated critical and 2 high by Mozilla.^[1] The 2 critical and high ones are:

Flaw	Severity	What Mozilla calls it
`CVE-2026-10701`	High	Incorrect boundary conditions in the Graphics: Text component
`CVE-2026-10702`	High	JIT miscompilation in the JavaScript Engine: JIT component

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 152 or later.

Before and after

After: Firefox 152, 16 Jun 2026, 40 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 151.0.3”, 2 Jun 2026.