I don’t like Firefox constantly updating the version or the Add-ons all by itself without my knowledge. I like to disable this. You can enable or disable this feature with these steps.
1. Click Firefox > Options > Options or if you have the Menu Bar enabled, select Tools > Options.
2. Click on the Advanced option along the top.
3. Click on the Update tab.
4. Uncheck the boxes under Automatically check for updates to: to disable the automatic updates. Check them if you wish for them to be enabled.
Alternately you may choose to select the Ask me what I want to do option under the When updates to Firefox are found: section.