Apple has patched 13 vulnerabilities in Safari with an update that takes the browser to version 3.1. But a security analyst has expressed concern about Apple still patching so many bugs in a "dot-release" operating system.

The new Safari, which Apple also proclaimed "the world's fastest web browser for Mac and Windows PCs," fixed the same 10 flaws in the Mac and Windows editions, and three more in Safari for Windows XP and Windows Vista. Most of the 13 vulnerabilities were cross-site scripting bugs.

However, Andrew Storms, director of security operations at nCircle Network Security, warned that Apple "has to be careful" releasing updates like this.

"Safari may not have any more bugs, and fixes, than IE and Firefox, but unleashing a giant package like this is going to create worry among users. When you release a dot-release version and it comes with a motherlode of vulnerabilities, that can bring down the favourable relationship that Apple has with its users," Storms said.

Only one of the patched bugs carried Apple's most dire warning, that it could result in "arbitrary code execution." Unlike competitors such as Microsoft, Apple does not use a rating system to note the seriousness of individual vulnerabilities. Most vendors, however, rank flaws that let attackers execute malicious code as "high" or "extremely high."

Nine of the vulnerabilities - eight on Mac OS X - were classified by Apple as cross-site scripting flaws, which are often used by phishers and other identity thieves, but in some cases can be used to plant malware, a Trojan horse, perhaps, on a machine.

It's easy to dismiss cross-site scripting bugs, warned Storms, but doing so misses the big picture. "We've come to learn that cross-site scripting vulnerabilities are not the worst of the possible scenarios. But you have to understand where researchers are coming from. They're concentrating on cross-site scripting vulnerabilities, as well as other client-side [bugs]. It's all browsers these days."

Apple spelled out the details of the 13 bugs in a security advisory that accompanied the Safari 3 .1 update. The updated browser can be downloaded in versions for Mac OS X 10.4 (Tiger), Mac OS X 10.5 (Leopard), Windows XP and Windows Vista from Apple's website.