Updated July 29th, 2026: After Firefox 153 released, some users ran into browser crashes that occurred when certain internal Firefox files couldn’t be loaded or when launching following a browser update. Mozilla’s recommended fix is to download a fresh copy of the Firefox installer and re-install Firefox over the existing, corrupted installation. Saved user data—such as bookmarks and passwords—will be preserved, as they’re stored elsewhere, according to Mozilla.
Firefox 153 for Windows, macOS, Linux, and Android (see the announcement and release notes) brings several usability improvements, such as HDR video playback, isolated tab environments, and QR code generation for sharing links. Mozilla has patched more than 60 security vulnerabilities, and updates are also available for the ESR versions.
What’s new in Firefox 153?
For Windows users, Firefox 153 offers playback of HDR (High Dynamic Range) videos, although it does require that HDR mode is enabled in the Windows display settings. Laptop screens that only support “HDR video streaming” are not currently supported, nor are smartphone videos in portrait orientation.
With the built-in PDF viewer and editor, you can now merge multiple PDF files by dragging them into the PDF sidebar. You can also insert images as new pages into PDF documents.
If you want to share a link—for example, with your own smartphone—without using a web service (such as Firefox Sync), you can generate a QR code now. Firefox highlights the location-sharing icon in red when a website has access to your location.
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The free VPN introduced with Firefox 149 continues to offer a selection of virtual locations, temporarily expanded to 28 countries with unlimited data (until the end of August). The free VPN is currently available to Firefox users in the US, UK, Canada, France, and Germany.
Security updates in Firefox 153
In the Security Advisory 2026-68, Mozilla lists over 63 security vulnerabilities that have been fixed, 60 of which were discovered and reported by external security researchers, including three by OpenAI Codex Security. Mozilla classifies 17 of these vulnerabilities as high risk, and four of them pose a risk of escaping the browser’s sandbox.
A further 35 vulnerabilities are classified as medium risk, with the remainder classified as low risk. The final three entries in the security report summarize an unspecified number of internally discovered vulnerabilities classified as high risk, resulting from programming errors in memory management. The vulnerabilities are grouped according to which apps and app versions are affected.
Tip: Whether you keep your browser up to date, you need proper antivirus protections if you want your PC to remain secure and private. Check out our picks for the best antivirus software for Windows as well as best VPN services to stay ahead of security problems.
Other Firefox browser updates
The ESR versions of Firefox have also been updated to 140.13.0 and 115.38.0. However, the latter is only available for Windows 7 and 8.1, and macOS 10.12 to 10.14.
In the ESR versions, Mozilla has fixed the aforementioned vulnerabilities that were already present in their code from generations past. That amounts to at least 32 security vulnerabilities patched in Firefox 140.13 and at least 14 in Firefox 115.38, and these include two vulnerabilities classified as critical.
Firefox 153 forms the basis for the next ESR generation, which means Firefox ESR 140 will be replaced by Firefox ESR 153 this October.
Meanwhile, Firefox ESR 115 will continue to receive security updates until March 2027 (v115.52), according to this support page. As that deadline creeps up, Mozilla will once again reassess the situation and then decide whether to extend the grace period again or not.
