EDIT: problem solved! Thanks a lot for the help!! 
Hey. I have a weird issue with Photoshop, could I ask you guys for some help with it?
I have the impression the quick mask tool has, erm, well… has broken. Either it’s a Mandela effect and I’m remembering wrongly how it should be working, or I’m not mistaken and something is wrong with the way it’s working for me now.
The way I think I remember it, and the way I think it should be working: I open an image, prop up the quick mask, paint the areas I want with my paint brush, exit the quick mask, those areas are selected, the end. Or I would select all before running the quick mask, and the areas I paint would be the only ones not selected.
The way it’s working now… it’s confusing to me, frankly.
I captured a photoshop session, here’s what it looks like, you may want to click to have the video in fullscreen rather than embedded in the post:
I found only one settings panel for the quick mask, and toggling both available options won’t change the issue, I can’t work on an image, just open it and immediately use quick mask to paint areas, I first need to select a smaller part of the image to exclude/include parts into it.
I must ask you: am I becoming mad, or has the quick mask, really, gone bad?
And of course, would you know how to revert it to normal?
Thanks if you can help ^^
EDIT: problem solved! Thanks a lot for the help!!