Something to check:
Sometimes when you watch videos from certain sites they require "codex" to be installed supposedly to decode the video. That so-called codex is actually just a script that will show you ads everywhere you go on the internet - no matter the site - you would need to find the installed codex and delete it (which will unfortunately, also disable the video.) The same might apply to any software you recently installed - the software might have installed adware.
In these cases, the sites (like itch.io) earn no revenue and have no control over the ads - the scammers who got you to install the codex are the ones making money.