Firefox 0day local file reading

RSnake mentioned a potential way to read security sensitive configuration settings from Firefox on ha.ckers.org, with an example PoC from Sergey Vzloman that used the resource:// URL protocol handler in Firefox. Unfortunately, the settings that were read were the default settings inside the Firefox install directory.

An example resource URL would be resource://gre/greprefs/security-prefs.js which reads the security-prefs.js file from your Firefox install directory, which on Windows could be C:\Program Files\Mozilla Firefox\greprefs\security-prefs.js. Mozilla must have acknowledged the potential for directory traversal here, as they have blocked any attempts at including the string ..\ or ../ inside resource: requests.

BK demonstrated in the thread that Mozilla does not properly sanitize the input properly, and that you can circumvent this restriction by using ..%5C instead of ..\ which means that you can read arbitrary files from the local system by exposing the file contents as readable properties on SCRIPT or CSS tags.
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