A security researcher who found a major vulnerability in eBay's website last week said a second flaw he found hasn't been fixed and could be used to hijack user accounts.Jordan Lee Jones, a 19-year-old college student who lives in Stockton-on-Tees, U.K, said he notified eBay on Friday by email of the second vulnerability. It hadn't been fixed as of Monday, so he decided to publish details of it on his blog.