As was mentioned here several times... Install uBlock Origin in your browser. That will kill most of those annoying messages.
I have uBlock, universal bypass, and clearURLs and they only stop the messages about extensions. It does nothing to prevent the antivirus/browserguard from freaking out. With Malwarebytes it tries to block the page, so I tell it to allow, then it tries to prevent a DL window from opening, so I allow it, and then sometimes it causes the download itself to fail, claiming the file contains a virus (it doesn't). Malwarebytes is known for overreacting, but there is something about LetsUpload that's sketchy as fuck.
Interesting... I've not had any of those issues with the links. I stopped using Malwarebytes because it blocked most of what I wanted to see. It usually managed to screw something up for me. I occasionally use it on demand though. I use Firefox... I don't have clearURLs, but I do have Adfly skipper, and use Anti-Adblock Killer script for Tampermonkey. I also have the popup blocker in FF active. (That may be why I don't see what you see. Not sure though.) I agree Letsupload is not the friendliest. Just tried it again, and the worst I get is a warning from FF that says the page tried to redirect me to another url... No browser extension request. (I've gotten plenty of those in the past) Wish I could be more help.
