Actual the latest ESR version is 52.1.0, released during the past day. ESR stands for Extended Support Release. It is a special release and primarily meant for companies, but this release can also be used by users who need to use plugins other than Flash like the Java plugin.

• https://www.mozilla.org/en-US/firefox/organizations/

Firefox 52+ releases only supports the Shockwave Flash plugin and disables all other plugins. You can consider to use the Firefox 52 ESR version if you need to use other plugins.

• https://support.mozilla.org/en-US/kb/npapi-plugins

See also:

• https://www.mozilla.org/en-US/firefox/organizations/all/
• https://www.mozilla.org/en-US/firefox/organizations/notes/
• https://www.mozilla.org/en-US/firefox/organizations/system-requirements/

Thanks cor-el, you have superman/woman skills!

I guess I'll not worry, unless something that used to work does not now. I'm surprised I got this update notice (received today), as I am a home user, never a power user, and I already have 52.0.2 installed from the last update, I don't recall exactly when.

Could have FF noticed I have something on my computer which would require the esr version, thus sending me the update, or did everyone get this update notice? This is more thinking out loud and does not need a reply.

I got an esr notification for the regular release on Windows 7 (screenshot attached comparing the Troubleshooting Information page). I think it's a temporary glitch because the proper next version for me is 53.0. Hopefully will be cleared up at some point today.

I received the same thing yesterday and today. I have 52.0.2 standard/release. Out of the blue, Firefox prompted me to update to 52.0.2esr. I went ahead with the update, which proceeded to download then ask me to restart. Once I restarted firefox, it told me the update failed and prompted me to download firefox manually. I ignored it at that point and went back to what I was doing.

Now today, my laptop has just gone through the exact same procedure. However, after the restart and subsequent failure message, I went to the about page and was prompted to download/install 53.0 (release I'm assuming). I'm about to restart now, fingers crossed. It sounds like something screwy is going on with the updater.

Edit: So I think what cor-el was trying to say is that if Firefox thinks we're using plugins that require NPAPI support, then the updater will automatically choose the esr channel instead of the release channel. Please correct me if I'm wrong? If so this should probably be explained in the surprise update...

Only the Windows XP and Vista users should be getting a update to Firefox 52 ESR if they are not using it already.

James said

Only the Windows XP and Vista users should be getting a update to Firefox 52 ESR if they are not using it already.

Hmm, definitely sounds like something funky is going on here then.