Most browsers attempt to see through obfuscation techniques to identify unsafe Web addresses. But in Firefox obfuscated URLs go inside of iFrames, blocks of HTML code that add content to a Web page from a third party’s server.
Armorize, a security company, said in a blog post, “A bug has been noticed in all versions of Firefox that fails to generate an alert when an obfuscated URL is being placed in iFrames. In certain cases, the vulnerability can be used effectively in spreading malware and stealing sensitive information.”
The company also posted a generic proof-of-concept exploit to demonstrate the flaw.
Dennis Fisher, Security Researcher, Kaspersky Lab, said, “URL obfuscation and the misuse of iFrames are not new techniques, but they can nevertheless be combined effectively to dupe potential victims.”
Mozilla’s bug tracking system, Bugzilla, has an entry for the vulnerability, 570658, which indicates that a fix is underway.
Johnathan Nightingale, Director, Firefox development said, “The concern expressed in the bug is that a page could be constructed with an embedded iFrame that uses a confusing URL. Most users don’t look at the HTML source of the pages they are loading, which is the only way you’d encounter this URL. We do not anticipate this bug would cause user confusion or deception. Firefox ships with built-in phishing and malware protection that warns users if they are attempting to visit a dangerous URL.”