To disable updates in Firefox, do the following: 1. Close Firefox 2. Open the Registry Editor a. Press the Windows Key + R b. Type regedit and hit Enter.
1. Click the menu button and select Options.Preferences. 2. In the General panel, scroll down to the Firefox Updates section. 3. Check Never check for updates.
Stop/close Firefox, then open up the Windows Registry Editor (regedit.exe) and navigate to the following key: HKEY_LOCAL_MACHINE -> SOFTWARE -> Policies.
My Firefox is currently on version 68.0.2 and is badly out of date. The about:policies page says there is a policy called DisableAppUpdate with a value of True.