For decades, WinRAR has been the go-to software for opening and creating RAR files. Even though Windows 11 now natively supports the RAR format — removing the need for most people to install third-party archiving tools — millions of users worldwide still rely on WinRAR, often out of habit or for its extra features. But if you're one of them, you'll want to pay attention: a recently discovered security flaw is being actively exploited, and it could allow hackers to run malware on your PC as soon as Windows starts.