May 17, 2020

Another day, another Firefox release

Mozilla released version 16 of its popular web browser only a few weeks ago and since then it has had two point releases to fix security issues. The latest release, 16.0.2 adds fixes for problems with the Javascript location object.

Three separate issues with the Javascript Location object where reported to Mozilla and fixed in this release:

  1. Security researcher Mariusz Mlynski reported that the true value of window.location could be shadowed by user content through the use of the valueOf method, which can be combined with some plugins to perform a cross-site scripting (XSS) attack on users.
  2. Mozilla security researcher moz_bug_r_a4 discovered that the CheckURL function in window.location can be forced to return the wrong calling document and principal, allowing a cross-site scripting (XSS) attack. There is also the possibility of gaining arbitrary code execution if the attacker can take advantage of an add-on that interacts with the page content.
  3. Security researcher Antoine Delignat-Lavaud of the PROSECCO research team at INRIA Paris reported the ability to use property injection by prototype to bypass security wrapper protections on the Location object, allowing the cross-origin reading of the Location object.

Mozilla also released a new version of its Thunderbird email cleint but noted that Thunderbird is only affected by window.location issues through RSS feeds and extensions that load web content.

The latest version can be downloaded from here while the release notes for 16.0.2 are available from

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