Hi

If you type about:preferences#advanced into the address bar and select the Update menu, you will see the options you need to turn off automatic updates.

I strongly recommend you keep Firefox up to date, as that is the best way to get new features and any security fixes. You can read how to do a manual update check here.

I hope this helps, but if not please come back here and we can look into a different solution for you.

See also:

• https://www.mozilla.org/security/known-vulnerabilities/firefox.html

You can consider to use the Firefox 38 ESR version. Current is Firefox 38.3.0 ESR (38.4.0 is slated for next Tuesday):

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

• https://www.mozilla.org/en-US/firefox/38.3.0/releasenotes/
• https://www.mozilla.org/en-US/firefox/organizations/system-requirements/

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:37.0) Gecko/20100101 Firefox/37.0

Is this the version you are indeed using? or maybe the useragent was set to this version even if using current Release.