Firefox 30 installed itself WITHOUT permission and I am SEETHING.

Question

I'm on XP. I have Firefox set to let me know when there are updates, but to let me manually choose to install them. I had Firefox 28. It kept bugging me multiple times a day, usually when I was in the middle of something, to first install 29 and then 30.
I NEVER let it.
I came back from a break, pressed the space bar, and a Firefox pop-up was on the screen saying it was downloading an update. I pulled the wire cable connecting to the internet out, severing any connection, but it was too late. Firefox said it was installing update.
When I install updates from Firefox I use portable apps so I know it doesn't insert itself into other directories. This keeps my machine clean. I did not ask for or want an auto update.
What Happened?
Is this a new Mozilla policy, to badger users many times a day and then install even if they say, "No"?
Is there a virus in some new Firefox programs?
I run multiple antivirus scans, and don't think I have anything bad on my machine.

Answer 1

Thank you, Tyler. Yes, there is an important reason(s) I don't always upgrade.
Stability. The value of my time. Privacy.
With respect, every software maker thinks his or her company is the most important software on my computer (and rightly so... to an extent). I'd say 90% or more of the updates have no effect on the way I use my machine, but say, a 10%* probability of causing a conflict with other things on it that will require hours, sometimes days of my time to resolve, which your company is not going to pay me for. Very little or no accurate or complete information is provided as to what a given update will do.
*10% chance of problem means each update has a 90% chance of updating with no problem. Then after just 5 program updates (I'm talking about any combination of programs on my machine, not just Firefox) my reliablity is, what .9x.9x.9x.9x.9 = .59? You can see how stability drops rapidly for the user who regularly updates all of his or her programs all the time. And that doesn't count potentially unique plug-ins.
In this instance I just finished re-building my computer after hardware faults were causing it to randomly shut-down. This took hours of time over several days trying to troubleshoot. Took everything apart, checked, cleaned, reseated things and rebooted.
Then once I finally get it stable, Firefox after nagging and nagging and nagging and nagging and nagging and nagging (get it- nagging?) for 29 goes and upgrades itself to 30 without me being able to take a snapshot of my registries or doing the protective back-up steps I normally take before bracing myself and going through a round of multiple software upgrades as a part of regular maintenance.
I tend to respect Mozilla, but it is turning into a nagging shrew of a program. If it continues to take time away from my work, which by the way is not for Mozilla, volunteer or otherwise, I'll have to research and find something that works better for me.
I am particularly fearful and suspicious of any program that takes liberties with my system without my permission, as Firefox apparently just did. I am less likely to let a program like that on my machine at all.
As for the actual upgrade, there's nothing I can really do about it now, is there? I didn't object in theory, but you didn't give me the choice.
Please leave this post visible in case someone else experiences the same issue of Firefox upgrading itself without apparent permission.
Thank you.
PS, Assuming it is complete and accurate, It is good to know that Firefox installs in only one location (eg. no floating dlls, history files, etc) similar to using portable apps.