This article takes a while to say that all browsers, except possibly Internet Explorer 8, are vulnerable to a simple attack that will cough up any data you have in your auto-complete file. That is, names, password, credit data? (who keeps credit card data in auto-complete? Have you checked your auto-complete file recently?)
Read the article: Auto-complete: browsers disclose private data – Update
Comments on original proof of concept site says some Mac OSX systems are giving the data, yet some not, even with Auto-Complete turned on.
Advice: Turn off Auto-Complete in all browsers until this is solved…regardless of what a pain in the ass this is. Oh, and don’t go to those hacker sites.