The AppleScript Editor in Mac OS X 10.3.9 does not properly display script code for an applescript: URI, which can result in code that is different than the actual code that would be run, which could allow remote attackers to trick users into executing malicious code via certain URI characters such as NULL, control characters, and homographs.
http://www.vupen.com/english/advisories/2005/0455
http://www.securityfocus.com/bid/13480
http://secunia.com/advisories/15227
http://lists.apple.com/archives/security-announce/2005/May/msg00001.html