Download Firefox 12-51 52 Esr -

Click into the version folder, then select:

If you are downloading for a corporate environment, avoid standard version 52.0. You want 52.x.x ESR.

The ESR (Extended Support Release) is designed for organizations. While standard Firefox 52 received security updates only until September 2017, Firefox 52 ESR received security updates until September 2018. For Windows XP users, Mozilla extended this specifically to 52.9.0 ESR. Download Firefox 12-51 52 Esr

Critical note for 52 ESR users: If you install Firefox 52 ESR, you must immediately disable automatic updates. Otherwise, it will auto-upgrade to Firefox 60 ESR (which drops NPAPI support and will break your legacy plugins).

How to disable updates in 52 ESR:

Warning: These versions have unpatched security vulnerabilities. Only download them for air-gapped machines, virtual machines, or specific legacy tasks. Do not use them for online banking or logging into modern social media.

Mozilla does not host these old versions on their main website (mozilla.org). They use a dedicated archive. Here is the safe method to download. Click into the version folder, then select: If

Select your language (e.g., en-US). Download the installer file ending in .exe (for Windows) or .dmg (for Mac).

Direct Download Examples (for reference): While standard Firefox 52 received security updates only

Do not use these versions for everyday browsing – they have unpatched critical security vulnerabilities. Use them only for: