Hi

To be fair, Apple quite possibly stopped supporting that operating system some time ago, so you have likely not had security updates for quite a while now.

Firefox kicks me out! But now my favorite browser (FF) quits support. I'm amazed that a project like Mozilla does not care about sustainability. So why is ESR for Macos 10.9 to 10.11 not supported anymore?

Mozilla did not stop supporting the old eol macOS 10.9, 10.10, 10.11 recently. They stopped supporting back on October 5, 2021 when the last Firefox 78 ESR update was released as in 78.15.0esr https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr

Firefox 79.0 to 115 ESR requires macOS 10.12, 10.13, 10.14 to run while Firefox 116.0 or later requires macOS 10.15 or later to run. https://support.mozilla.org/en-US/kb/firefox-users-macos-1012-1013-1014-moving-to-extended-support

Mozilla does care about sustainability. They supported the then eol Windows XP/Vista (with Firefox 52 ESR, 52.9.0esr) for over two years after Chrome/Chromium based browsers dropped WinXP/Vista yet many WinXP users were not happy and wanted Mozilla to spend resources to support for more years. They supported the old macOS 10.9, 10.10, 10.11 when Chrome/chromium based browsers dropped support.

Now Mozilla is using the old Firefox 115 ESR branch and continuing with updates until Fx 115.21.0esr in March 2025 so the Windows 7, 8, 8.1 and macOS 10.12, 10.13, 10.14 users can still be supported as these builds are not intended for Windows 10/11 and macOS 10.15+ users. The Chrome/Chromium based browsers dropped Windows 7, 8, 8.1 back in Jan/Feb of 2023 though they did support macOS 10.12 to 10.14 for a bit longer. Originally the old Firefox 115 ESR was going to end at Fx 115.15.0esr but Mozilla revealed at almost last day that they were extending updates. They are going to decide in early 2025 on whether they extend updates again.

Btw on March 14 any extensions you have installed in Firefox may not work https://support.mozilla.org/en-US/kb/root-certificate-expiration

Thanks James and Paul, sorry for my kind of aggressive post here - I thought thats the only way to get sombodies attention. I'll check my extensions, when the time comes in '25. Concerning security updates the machine is behind a firewall, I had no incidence the last 10 years. Actually I'm running legacy software on that machine, that is incompatibel with with newer OS. That's why I stick to 10.9. But certainly sooner or later the time will come...;-( Thanks for your complete explanation of the situation!