You can enable the '''ManualAppUpdateOnly''' enterprise policy, documentation is linked in [https://support.mozilla.org/en-US/kb/see-active-policies-firefox-enterprise about:policies].

Thanks for the reply, but unfortunately enterprise policies aren't enabled on my browser so this doesn't help.

Enterprise policies can be enabled on any browser that you have control over.

See also: *https://github.com/mozilla/policy-templates/tree/master/mac

''<p>julian.templeman [[#question-1446052|said]]</p>'' <blockquote>I've got a really old MacBook Pro that's still running 10.13, and Firefox has started displaying a nag screen telling me that this version is no longer supported, and to install a newer version of MacOS. </blockquote>Are you using Firefox 115.x.x ESR (current is 115.10.0esr) or the 115.0.3 Release? as the Fx 115 ESR should not be getting nags that the version is no longer supported when it is still getting updates. The last major update for Fx 115 ESR will be 115.15.0esr in September 2024. https://www.mozilla.org/firefox/all/#product-desktop-esr https://support.mozilla.org/en-US/kb/firefox-users-macos-1012-1013-1014-moving-to-extended-support The most current you can use on macOS 10.12, 10.13, 10.14 is Fx 115 ESR as Firefox 116.0 and later requires macOS 10.15 or later to run.