On Friday, February 21, Apple issued a security update for iOS (iPhone, iPad, iTouch).
On Tuesday, February 25, updates for Macs running OS X were released (MacBook, iMac).
The security vulnerability was making it possible for hackers to monitor the exchange of potentially sensitive communications. Without the fix, a hacker could impersonate a protected site and sit in the middle, between your device and the website you are connecting to (your bank, your email server, etc) as email or financial data passed between you and the website. The vulnerability would allow the hacker to intercept the information as it passed. These updates will fix the vulnerability related to SSL/TLS, or Secure Socket Layer and Transport Layer Security.
The security flaw Apple is addressing involves verifying security certificates, the part of the process that involves making sure a site is really who it says it is. You may have noticed a padlock icon in your browser, or seen "https" at the beginning of a URL when visiting a website, both of which indicate that you have a secure, private connection. The failure to verify these security certificates means that https sessions on public Wi-Fi, and even some unsecure private Wi-Fi networks may be vulnerable to hackers.
The security updates that patch the vulnerability for OS X Mavericks, Safari, Apple TV, and iOS 6 and 7 are available now. If you have not already updated your Apple products to apply these updates, please do so immediately.