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Mozilla Foundation Security Advisory 2007-09

Title: Privilege escalation by setting img.src to javascript: URI
Impact: Critical
Announced: March 5, 2007
Reporter: moz_bug_r_a4
Products: Firefox 1.5.0.9/2.0.0.1, SeaMonkey 1.0.7

Fixed in: Firefox 2.0.0.2
  Firefox 1.5.0.10
  SeaMonkey 1.1.1
  SeaMonkey 1.0.8

Description

moz_bug_r_a4 reports that the fix for MFSA 2006-72 in Firefox 1.5.0.9 and Firefox 2.0.0.1 introduced a regression that allows scripts from web content to execute arbitrary code by setting the src attribute of an IMG tag to a specially crafted javascript: URI.

The same regression also caused javascript: URIs in IMG tags to be executed even if JavaScript execution was disabled in the global preferences. This facet was noted by moz_bug_r_a4 and reported independently by Anbo Motohiko.

Thunderbird is not affected by this flaw as it will not execute javascript: URIs in IMG tags.

Workaround

Upgrade to a version containing the fix. Disabling JavaScript does not protect against this flaw.

References