Last week, Mozilla removed the latest version of their Firefox Web browser just a day after it was released. The reason? A security vulnerability was discovered after the browser had shipped. Initially, Mozilla did not disclose the technical details of the vulnerability, but laconically stated “The vulnerability could allow a malicious site to potentially determine which websites users have visited and have access to the URL or URL parameters”. Since Mozilla has given us little to work with, we will dive into the technical details of the vulnerability.
In the case of the Firefox 16 vulnerability, the same origin policy is our culprit.
However, in Firefox 16 the same origin policy was not implemented correctly and allowed the attacker to gain access to the URL, allowing the leakage of personal data such as the victim’s Twitter ID in this case.