Mozilla Foundation Security Advisory 2013-75

Local Java applets may read contents of local file system

August 6, 2013
Georgi Guninski, John Schoenick
Firefox, Firefox ESR, SeaMonkey, Thunderbird, Thunderbird ESR
Fixed in
  • Firefox 23
  • Firefox ESR 17.0.8
  • SeaMonkey 2.20
  • Thunderbird 17.0.8
  • Thunderbird ESR 17.0.8


Security researcher Georgi Guninski reported an issue with Java applets where in some circumstances the applet could access files on the local system when loaded using the a file:/// URI and violate file origin policy due to interaction with the codebase parameter. This affects applets running on the local file system. Mozilla developer John Schoenick later discovered that fixes for this issue were inadequate and allowed the invocation of Java applets to bypass security checks in additional circumstances. This could lead to untrusted Java applets having read-only access on the local files system if used in conjunction with a method to download a file to a known or guessable path.

In general these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled, but are potentially a risk in browser or browser-like contexts.