I found out about this on Tumblr but I made sure to look up shit first... y'know because it's the internet. And Tumblr has a nasty reputation about panicking over stuff without doing the research.
However, looks like this one's legit. It's called the Heartbleed Bug and it's a major flaw in OpenSSL encryption, meaning the wrong people can steal your private information that OpenSSL is meant to try and protect.
you can read up here at heartbleed.com
In the meantime, you might want to hit up your various hangout spots and change your passwords. Especially places involving financial or personal information.
Wanted to give my boos a heads up.4/9/14 Update:
Okay, as a heads up since I couldn't update earlier today, if any sites you visit are vulnerable to the Heartbleed bug, changing your password may not do much thanks to the vulnerabilities it creates. But there is good news. You can test sites to see if they're vulnerable or not now!
Go to filippo.io/Heartbleed/
and type your name in the test bar and click the big green go! button, and the site will fill you in on whether or not the site you provided is vulnerable. If it is, don't change any passwords until you know for sure it won't be compromised. If it's all clear, you may not have to change the password but it never hurts to cover your ass.