Last Friday, Apple announced a serious security issue that will require anyone with an iPhone, iPod, or iPad running iOS 6 or 7 to update their system. The security hole could allow hackers to access transactions that you make on your mobile device or computer through a public wireless network (WiFi). The security hole will make an unsecure connection appear to be secure. The update will fix this vulnerability, and it is recommended that you do it immediately.
For your desktop and laptop Macs, there is currently no update to install, but it is recommended that you download either Chrome or Firefox and stop using Safari as your web browser. You should also avoid public wireless networks (like coffee shops and airports). Apple is supposedly working on a security update for OS X Mavericks.
Switching browsers on your mobile device will not fix the problem, as Chrome and Firefox use the same security background as Safari for mobile devices. Only installing the update will patch the security hole.
Find more information from Apple here: http://support.apple.com/kb/HT1222
Instructions to update your device can be found here: http://support.apple.com/kb/ht4623