It seems as though every week or so there’s a new hack or exploit that reveals millions of passwords or important data from a popular web service, and this week is no exception. On Tuesday, IT professionals got word of a serious flaw in OpenSSL — the browser encryption standard used by an estimated two-thirds of the servers on the internet. The flaw, which was dubbed “Heartbleed,” may have exposed the personal data of millions of users and the encryption keys to some of the web’s largest services. Here’s what you need to know:

What is Heartbleed?

It’s a bug in some versions of the OpenSSL software that handles security for a lot of large websites. In a nutshell, a weakness in one feature of the software — the so called “heartbeat” extension, which allows services to keep a secure connection open over an extended period of time — allows…