CSP bypass due to permissive Reader mode whitelist

ID MFSA2015-118
Type mozilla
Reporter Mozilla Foundation
Modified 2015-11-03T00:00:00


Security researcher Mario Heiderich reported an issue where the security protections of Reader mode in Firefox can be bypassed, allowing scripts to be run. Mozilla developer Frederik Braun independently discovered and reported this same issue as well. This issue happens even though Reader View explicitly disables script for rendered pages through a whitelist of allowed HTML content. Mario discovered that the whitelist was too permissive and a malicious site could manipulate content to bypass CSP protections, allowing for possible cross-site scripting (XSS) attacks.