XSS hazard in multiple character encodings — Mozilla

Security researchers Yosuke Hasegawa and Masatoshi Kimura reported that the x-mac-arabic, x-mac-farsi and x-mac-hebrew character encodings are vulnerable to XSS attacks due to some characters being converted to angle brackets when displayed by the rendering engine. Sites using these character encodings would thus be potentially vulnerable to script injection attacks if their script filtering code fails to strip out these specific characters.