Canvas allows the use of the "feDisplacementMap" filter on images loaded cross-origin. The rendering by the filter is variable depending on the input pixel, allowing for timing attacks when the images are loaded from third party locations. This vulnerability affects Firefox < 50.
https://www.mozilla.org/security/advisories/mfsa2016-89/
https://bugzilla.mozilla.org/show_bug.cgi?id=1298552