Oh, great. Computer security researchers have developed a proof-of-concept for a type of ransomware that would act when you try to *upload* a file. It would be able to encrypt any files in the folder you uploaded from, and any subfolders of it.
This is a proof-of-concept; the researchers have not seen any such attacks in the wild. But stay careful out there, okay?
Affects Chrome and Edge, but *not* Firefox or Safari!