Secunia has posted a security advisory for a “highly critical” vulnerability found in Apple’s Safari Web browser that could potentially allow malicious Web sites to compromise a vulnerable system. “The problem is that the ‘help’ URI handler allows execution of arbitrary local scripts (.scpt) via the classic directory traversal character sequence using ‘help:runscript,'” explains the security firm. “It is reportedly possible to place arbitrary files in a known location, including script files, on a user’s system if the Safari browser has been configured to (‘Open safe files after download’) (default behavior) by asking a user to download a .dmg (disk image) file.”