Often you find a neeed to keep an old copy of Firefox around for testing or to use a specific plugin (Example: Selenium). In these cases it can often prove problematic to allow the browser to auto-update. Here are some simple steps to prevent this behavior.
Enter “about:config” into the Firefox URL bar, then change the following values. You can click on them to toggle.
app.update.auto = false
app.update.enabled = false
Alternately, on Windows you can edit the config file at: %APPDATA%\Mozilla\Firefox\Profiles\
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