The XPCVariant::VariantDataToJS function in the XPCOM implementation in Mozilla Firefox 3.0.x before 3.0.15 and 3.5.x before 3.5.4 does not enforce intended restrictions on interaction between chrome privileged code and objects obtained from remote web sites, which allows remote attackers to execute arbitrary JavaScript with chrome privileges via unspecified method calls, related to "doubly-wrapped objects."