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Firefox administrator reference

Firefox 147 release notes for enterprise admins

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Firefox 147

Released 13 January 2026.

These changes apply to Firefox 147 and Firefox ESR 140.7.0 unless explicitly stated. Firefox ESR 140 is the current ESR, so enterprise changes are no longer backported to Firefox ESR 128.

Fixes

  • Private Window options were still available from the Firefox View tab when private browsing was disabled. (bug 2004669)
  • A performance regression affecting extension native messaging reached the ESR in Firefox ESR 140.7.0. In earlier Firefox 140-series builds, native messaging operations could experience significantly increased latency, affecting enterprise extensions that communicate with external processes. The release channel received this fix in Firefox 146. (bug 2002517)

Known issues

  • Using Trellix DLP Endpoint for Windows can cause crashes when dragging and dropping files. Set the security.sandbox.content.close-ksecdd-handle preference to false as a workaround.