How would proxy settings in browser become changed?

[freond1]

I ran Live Update in Norton Security Suite, and it failed with a message that proxy setting were changed in my browser in a way that prevented Live Update from running. It offered a fix, which ran quickly and then Live Update ran OK.

My question is how those proxy settings might have been changed? I don't touch them.

I primarily use Firefox, but have IE and Chrome installed. I don't know which browser Norton was referring to.

I should have researched what the proxy settings were on each browser before running the fix, but I didn't. I will next time. Sorry for not having that data, and I realize that at best I can get only a very general answer to my question. But that will do for now, if anyone can provide one. Thanks!