This issue is detailed here: http://www.contextis.co.uk/resources/blog/webgl/ The proof-of-concept consists in loading a cross-domain image as a WebGL texture, and rendering each pixel using a shader program that takes an amount of time proportional to the R, G, B values of pixels. By timing this, they get an approximation of the image. Upstream bug: https://bugzilla.mozilla.org/show_bug.cgi?id=655987
RHEL-4/5/6 ships firefox 3.6.x, which does not have support for WebGL. Statement: Not Vulnerable. This issue did not affect the version of Firefox as shipped with Red Hat Enterprise Linux 4, 5 or 6.