yahoo search sneaked into my mozilla recently, usually I can't tell but now, I'm seeiing some redirects...

Probably not simple, given rogue extensions or malware that redirect searches to something they monetize via affiliate links and similar make it hard to remove all of their traces, so there's a few places you might wanna look into. You either need to disable all addons and start enabling them one by one, or restart into Troubleshoot Mode to skip loading them all for a test. Then separately check your home page and search provider settings and addons. See support.mozilla.org/questions/1590908 for some links and context.