Note: Turning off the automatic update of Firefox is not recommended. Only the latest version of Firefox gets regular security updates and will keep you safe and sound on the internet.
However, if you really need to turn off the automatic update of Firefox, please follow these steps: In the Firefox window, click the menu button at the top right corner, then select the Options menu item.
- From the Options tab (window for previous than 38.0 firefox version), click the Advanced panel.
- In the Advanced panel, click the Update tab.
- Under Firefox updates, select Never check for updates.
- Close the Options tab (or click the OK button for previous than 38.0 firefox version) to apply the changes.
Please report back if this helped you.