Firefox keeps taking over default programs
A while ago firefox started to take over as the program for mailto:. I even tried to stop it by changing firefox mailto to use outlook. Didn't help. I don't often use mailto, but I noticed it when I started outlook it said it wasn't the default program for everything and asked if I wanted to set it. Kept happening. Eventually I looked into default options for outlook and found mailto was set to firefox.
THEN I opened a downloaded PDF from a different browser and it opened it in firefox. I have Nuance PDF. And yes, now often when I start that it tells me that it's not the default.
And yes, I have or set the program for PDFs in FF to be Nuance PDF.
Outside of stopping using firefox, how do I get it to stop inserting itself as the default program? YES, at times I set FF to the default browser; did some recent upgrade make it mean to also set it to the default for all programs, and how can I set it to the default browser (which I do for some things I want to run at times), without stealing all the progam defaults?
WIn7Pro, FF 78.0.1 (64-bit)