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Firefox 153

Released 21 July 2026.

These changes apply to Firefox 153 and Firefox ESR 153 unless explicitly stated. Firefox ESR 153 is the new ESR - enterprise changes are no longer backported to Firefox ESR 140. Policies listed under Firefox ESR 153.0.0 became available to ESR admins for the first time in this release.

New in Firefox 153

• DisableRemoteSettingsAndAcceptSecurityConsequences: Disable Remote Settings updates and accept the resulting security consequences. Only use this policy when the consequences are fully understood.

Changes

• Containers: Updated for the new container color palette. Existing color names are migrated to the new names automatically.
• Cookies: Behavior and BehaviorPrivateBrowsing accept partition-foreign, the new name for the reject-tracker-and-partition-foreign cookie behavior. Configurations using the old name continue to work.
• ExtensionSettings: Control extension host permissions using runtime_allowed_hosts and runtime_blocked_hosts, and control which permissions extensions may request using allowed_permissions.
• Users can no longer change the host permissions of Manifest V3 extensions installed using force_installed.
• ExtensionSettings: force_installed and normal_installed extensions can be installed directly from addons.mozilla.org when install_url is omitted.
• Homepage: Added a NewTabOnRestore option to open the default start page or about:newtab after restoring a previous session.
• ManagedBookmarks: Bookmarklets using javascript: URLs are now supported.
• Automatically discovered printers are now listed after manually configured printers in the print destination list. (bug 1996569)
• Firefox installed from a macOS .pkg package can now update without prompting for administrator credentials. (bug 1812480)

Fixes

• AutoConfig can once again set the browser.startup.homepage preference to a data: URL, fixing a regression introduced in Firefox 152. (bug 2047962)
• DisableSecurityBypass: The Allow download button was still shown when SafeBrowsing was set to false. (bug 1894373)
• ExtensionSettings: Extensions that were no longer permitted by allowed_types were not removed or blocked when the setting changed. (bug 2008100)
• ExtensionSettings: Individual Windows registry REG_SZ values overrode the JSON policy configuration when both were present. (bug 2048696)
• FirefoxHome: The policy was not reflected correctly in the redesigned Settings. (bug 2048048)
• PasswordManagerEnabled: The policy did not disable the Passwords sidebar panel. (bug 2041232)
• PopupBlocking: The policy did not lock all of the pop-up permission controls. (bug 1888477)
• SanitizeOnShutdown: The policy now correctly locks the History settings when configured. (bug 1888451)
• The Bookmarks and History sidebars could not be opened while the sidebar was hidden and PasswordManagerEnabled was set to false. This regressed in Firefox 153.0 and was fixed in a later Firefox 153 release. (bug 2056857)

New in Firefox ESR 153.0.0

• AIControls: Configure AI controls.
• BrowserDataBackup: Disable backup or restore of profile data.
• DefaultSerialGuardSetting: Control use of the Web Serial API.
• DisableRemoteImprovements: Prevent Firefox from applying performance, stability, and feature changes between updates.
• DisableRemoteSettingsAndAcceptSecurityConsequences: Disable Remote Settings updates and accept the resulting security consequences.
• IPProtectionAvailable: Prevent the built-in VPN from being available to users.
• LocalNetworkAccess: Configure local network access security features.
• RelaunchRequired: Require Firefox to be relaunched within a given period and notify the user of the upcoming relaunch.
• SitePolicies: Fine-grained control over policies for specific sites.
• VisualSearchEnabled: Enable or disable visual search.
• XSLTEnabled: Enable or disable support for the XSLTProcessor JavaScript API and the XSLT processing instruction.

Firefox 154

Released 18 August 2026.

These changes apply to Firefox 154 and Firefox ESR 153.1.0 unless explicitly stated. Firefox ESR 153 is the current ESR.

Firefox moves from a four-week to a two-week release cycle beginning with Firefox 155. Bug fixes, updates and features reach users more quickly once they are ready to ship.

New in Firefox 154

• CNSA2KeyAgreementEnabled: Enable the CNSA 2.0 ML-KEM-1024 key agreement for TLS. Does not apply to the ESR. (bug 2052296)
• DefaultBrowserSettingEnabled: Prevent users from changing the default browser. (bug 2051921)

Changes

• SanitizeOnShutdown: Added an Exceptions option to configure sites whose data should not be cleared on shutdown. Firefox 154 only. (bug 2049937)

Fixes

• SearchEngines: PreventInstalls did not prevent users from manually adding search engines in Settings or from the context menu. (bug 2052965)
• The -width and -height command-line options did not correctly set the Firefox window size. Firefox 154 only. (bug 1635927)
• Extended Protection (channel and service binding) for Windows SSPI authentication worked when using SPNEGO but not when using Kerberos directly. (bug 1179722)

Firefox 155 Latest

Released 1 September 2026.

These changes apply to Firefox 155 and Firefox ESR 153.2.0 unless explicitly stated. Firefox ESR 153 is the current ESR.

New in Firefox 155

• DisableLaunchOnLogin: This policy prevents Firefox from launching automatically when the user logs in (Windows only in 155). Does not apply to the ESR. (bug 2001734)

Changes

• SitePolicies: Added an HttpsOnly option to prevent specific sites from being loaded over HTTP. Firefox 155 only. (bug 2045980)
• Captive portal and network connectivity checks now use firefox-portal-detection.com instead of detectportal.firefox.com. Network allowlists and proxy rules naming the old domain need updating. Firefox 155 only. (bug 2049252, bug 1898891)

Fixes

• ExtensionSettings: In Firefox 154 and Firefox ESR 153.1.0, configurations that quoted booleans ("true") would break and an invalid entry discarded the whole policy. The validator is relaxed to accept quoted booleans again, and invalid entries are now individually skipped. (bug 2065965)
• SearchEngines: Contextual search prompted users to install a search engine when PreventInstalls was true. Firefox 155 only. (bug 2055614)
• Locking legacy preferences such as pref.general.disable_button.default_browser didn't disable the corresponding controls in Firefox Settings, following the Settings rewrite. (bug 2056928, bug 2055887)
• Firefox reported that it could pin itself to the taskbar when Windows Group Policy blocked pinning. Firefox 155 only. (bug 2059920)