This is very simple. Go to the second link provided by billmct. You'll download a zip file.
Extract the contents inside the zip file. In Windows you can right click the zip file and extract.
Now just double click on the "disable firefox updates" file.
That's it!
If for some reason you want the automatic updates feature turned back on again, then double click on the "enable firefox updates" file.
A computer reboot may be required for both actions.
In this screenshot I point to and highlight the file you need to double click on to disable that annoying pop up for automatic updates.
Keep in mind you'll eventually want to update. Mostly for security fixes. To do that you'll need the actual Firefox installer file. YOu can find that
here.
If you want a specific version, then you'll need to search through Mozilla's FTP directory tree. But! Don't installer an eailer version than the one you already have installed otherwise you'll probably end up with issues. For example, you have version 101 installed and the latest is 105. Don't install version 99. You'd chose versions 102 through 105. Hope that makes sense.
Here's the FTP directory tree of Firefox downloads:
Directory Listing: /pub/firefox/releases/
If you see a lower case "b", that means it's beta. You don't want that. "esr" means extended release. So for 100 you'd navigate to just the 100.0/ folder. Inside the 100.0/ you'll find different versions of 100 applicable to different operating systems and whatnot. Chances are you're instaled version is 32 bits. So you'd go into the 32 bitr folder. To confirm your installed version is 32, go to the top of Firefox, click Help and "About Firefox." You'll see the current version and whether it's 32 or 64 bit.
Now after you go into the 32 or 64 bit version folder you'll come across other folders for your language. In the U.S. you'll want the en-US/ folder. en obviously means English. Now just chose your installer type. I recommend the .EXE version. They're all the same Firefox download, it's just on how they install by Windows. I've read MSI installers can be problematic. If you noticed that the first installer is quite small, that's because it's a downloader stub. It'll fetch the download for you. I utterly hate downloader stubs because you never know what it's fetching behind your back. I'd rather download the whole installer myself...
= potential unneeded advice =
If you want to know how the PGP key and SHA256 sums work for file integrity and verification then ask. It's a dork thing, but is more of a way to know what you're downloading is in fact what you're downloading. In a nutshell, SHA256 hash checking can be done with the program HashTools (there are others), and PGP key verification can be done with Gpg4win which contains the Kleopatra UI (User Interface). PGP key verification can be done in the command prompt as well, but I hate the CMD prompt and Kleopatra makes it much easier. LOL
If you master Kleopatra you can now create your own public and private PGP key pair for encrypted communication. And Yes, you can type text in Kleopatra and have it encrypted. It'll also encrypt files.
Exchange
public keys with your recipients and you now have full on encrypted text in any communication platform. Your
private keys are just that -
private. They will unencrypt your text sent with your public key by your friends. So the private key absolutely needs to be guarded and never shared - with anyone!. The public key is just that - public! Those can be exchanged.
I believe the latest version of Thunderbird (an email client) has built-in PGP ability. But I don't particularly trust it. LOL! But that's just me and my gold plated tin foil hat.
Anyway, this bit of Info. not necessarily meant for you but for others as well...
BTW - This is exactly why one would want FDE (Full Disk Encryption. To guard private keys and the whole "enchilada"). I use this myself with the password stored in my memory and only my memory protected by the U.S. 5th amendment. I can NOT be tortured or compiled to give it up withen the jurisdiction of the United States.