Security firm Secunia said Monday that Apple Computeris Security Update released last Friday does not fully protect Mac users and that the company doesnit understand the seriousness of the issue.

"It is still possible to execute arbitrary code on a vulnerable useris system, just as easy as before Apple issued Fridayis security update for Mac OS X," Niels Henrik Rasmussen, CEO of Secunia, said in an e-mail to The Mac Observer.

Apple released a patch late Friday that fixed a hole in HelpViewer, preventing it from using scripts unless they are written by HelpViewer. The vulnerability made it possible to place arbitrary files, including script files, on a useris Mac if a browser had been configured to open files that appeared isafei.

Mr. Rasmussen said many problems still remain, however.

"What is really critical is the fact that Apple did not address the "disk" URI vulnerability, which allows malicious Web sites to silently place code on a useris system," said Mr. Rasmussen. "Everything should be OK, after the "help" vulnerability has been fixed, but another very unfortunate feature has been revealed in Mac OS X disk image and volume handling, allowing a disk image to register a new URI handler and associate an application with this - obviously this application can be located on the disk image or volume."

The result of this exploit, according to Secunia, is that malicious Web sites can exploit the "disk" vulnerability in the same way as the "help" URI handler, "still leaving all Mac OS X systems wide open for attacks," he said. "In other words, Mac users are as vulnerable now, as before the patch was released."

Secunia chastised Apple on two others fronts, saying the company has ignored the security breaches it addressed last Friday since February and that Apple isnit explaining to users through its updates just what the problem is and how serious it could be.

"Unfortunately, Apple once again fails to describe the severity of the issues fixed by the latest security update," said Rasmussen. "Apple states that the update iFixes CAN-2004-0486 to ensure that HelpViewer will only process scripts that it initiated.i. This does not clarify how important this update really is. Microsoft and most Linux distributions have learned the lesson and properly describe the nature and the impact of (most) vulnerabilities, allowing their customers to properly estimate the severity of a fixed issue. This is not possible when reading an Apple update." Representatives from Apple were not immediately available to comment for this story.

The description of the update, which is called Security Update 2004-05-24, is sparse on details, merely saying that it updates HelpViewer, one of the weak links in the vulnerability. The update is available via the Software Update control panel of Mac OS X.