I'm not going to pretend to understand what Capcom did to your PC with its last Street Fighter V patch, but by all accounts it was quite the boo-boo: it introduced a file that people could use to do bad things to your PC, in an excessively aggressive effort to combat piracy. Capcom promised a rollback of the patch, and now they've released a tool that will remove the offending file, if you were unlucky enough to have downloaded the patch in the first place.
The instructions are here, though note the bit at the top that states you might not need to go through this process. The issue affects "users who have downloaded the title update Ver.1.09 on 9/22, but have not applied the additional patch that became available on 9/23, as well as users who had not restarted their PC after applying the additional patch". Still, it's probably worth doing just to be sure.
To delete Capcom's insidious "rootkit", you'll need first to locate this new tool, which has been deposited on your PC via a Steam update for Street Fighter V, and then follow the above seven-part guide. Capcom warns that "obtaining this file through other sources can put you at risk of opening up your system to additional security risks. We ask that you do not download and execute files obtained by unknown sources".
