Howdy.
Having spent the last hour going through the various Twine and Itch.io forums/subreddits, I can't find a single reputable source talking about a security issue. It looks like one guy got a Trojan on their computer, one that is well-known and caught by up-to-date antivirus, and decided that Twine and Itch.io were at fault.
If you have additional information to share, please do, otherwise please stop spamming people's pages.