Except where noted, these changes apply to Firefox 151 and Firefox 140.11 ESR. Firefox 140 is now the current ESR, and enterprise changes will no longer be backported to Firefox 128 ESR.

Firefox 153 will be the next Firefox ESR release. As we approach that transition, fewer non-security fixes and enterprise policy changes will be backported to Firefox 140 ESR.

If you use the ESR, we strongly recommend testing with Firefox Beta or Nightly to identify any issues before the Firefox 153 ESR release.

Mozilla has introduced Firefox Support for Organizations, a new support offering for enterprise deployments of Firefox. For more information, see this blog post.

Other Changes

• Policy documentation has officially moved to https://firefox-admin-docs.mozilla.org/. Please update any existing bookmarks.

Bug Fixes

• The DisableRemoteImprovements policy was not reflected correctly in preferences. (Firefox 151 only)
• Sites blocked by enterprise policy did not display the correct error message. (Firefox 151 only)

Policies

• The XSLTEnabled policy has been added to enable or disable support for the XSLTProcessor JavaScript API and XSLT processing instructions. (Firefox 151 only)
• The LocalNetworkAccess policy has been added to configure local network access security features. This policy controls Firefox's behavior when websites attempt to access local network resources (localhost and local network addresses). (Firefox 151 only)
• The Preferences policy has been updated to allow setting preferences under the devtools. and sidebar. branches.
• The ExtensionSettings policy has been updated to support overriding update URLs. (Firefox 151 only)

Special Notes

We are extending Firefox 115 ESR support for Windows 7/8 and macOS 10.12/10.13/10.14 users until August 2026.