Something you might have heard of but have no clue about is the Heartbleed bug. It is among the major security vulnerabilities in the history of web and uses a breach in the OpenSSL standard to access essential data. Hackers can use Heartbleed to acquire very sensitive information such as credit card info, personal data and other important info. It is serious, but we are not helpless.
Companies like Facebook and Instagram have already issued a security patch, but we strongly advise that you change all your passwords as soon as possible. Use something like 1Password to help you manage your passwords. We do not know how many websites exactly have been affected by Heartbleed, but there's a simple way to find out. If you're on Chrome, you can download Chromebleed - a simple and easy to use extension that will notify you if a visited website is unsafe. Chromebleed is based on this great little tool developed by Filippo Valsorda and allows you to test any URL for the CVE-2014-0160 bug, widely known as Heartbleed.
In a few weeks Heartbleed will be a thing of the past. Web developers and security experts are working hard to fix the breach and even now, just a few days after it was discovered, it is only half as dangerous. However, because in situations like this it is better to blow cold, you should download and install Chromebleed. It's a free download from the Chrome Web Store.