A security researcher criticized Apple for what he called "foot dragging" over the DigiNotar certificate fiasco, and urged the company to quickly update Mac OS X to protect users.

"We're looking at some very serious issues [about trust on the Web] and it doesn't help matters when Apple is dragging its feet," said Paul Henry, a security and forensics analyst with Arizona-based Lumension.

Unlike Microsoft, which updated Windows Tuesday to block all SSL (secure socket layer) certificates issued by DigiNotar, Apple has not updated Mac OS X to do the same.

DigiNotar, one of hundreds of firms authorized to issue digital certificates that authenticate a website's identity, admitted on Aug. 30 that its servers were compromised weeks earlier. A report made public Monday said that hackers had acquired 531 certificates, including many used by the Dutch government, and that DigiNotar was unaware of the intrusion for weeks.

Because almost all the people who were routed to a site secured with one of the stolen certificates were from Iran, many experts suspect that the DigiNotar hack was sponsored or encouraged by the Iranian government, which could use them to spy on its citizens.

Microsoft isn't the only software maker to block all DigiNotar certificates: Google, Mozilla and Opera have also issued new versions of their browsers -- Chrome, Firefox and Opera -- to completely, or in Opera's case, partially prevent users from reaching websites secured with a DigiNotar certificate.

Users of Safari on Mac OS X, however, remain at risk to possible "man-in-the-middle" attacks based on the fraudulently obtained certificates.

And that rubbed Henry the wrong way. "Mac users have been left hanging in the wind," Henry said.

Because Safari relies on the underlying operating system to tell it which certificates have been revoked or banned entirely, Apple must update Mac OS X. The Windows edition of Safari, which has a negligible share of the browser market, taps Windows' certificate list: That version is safe to use once Microsoft's Tuesday patch is applied.

Henry admitted he wasn't surprised by the fact that Apple was odd-man out.

"No, I'm not, not after it took them a month to respond to the Comodo issue," Henry said, referring to a smaller-scale hack of another certificate authority last March.

Then, Apple updated Mac OS X on April 14, nearly a month after Comodo discovered the intrusion and began notifying browser makers. Microsoft had patched Windows to block the stolen Comodo certificates on March 23, while Google and Mozilla had even earlier.

The DigiNotar hack, however, was larger -- criminals acquired only nine certificates from Comodo -- and more serious in that the Dutch government relied on DigiNotar to secure its websites.

And then there are the boasts made by an unidentified hacker who has claimed responsibility for both the Comodo and DigiNotar breaches.

On Monday, that hacker -- known only as "Comodohacker" -- also asserted that he had penetrated four other CAs, or certificate authorities, including GlobalSign, a U.S.-based CA much more widely used than DigiNotar.

Tuesday, GlobalSign suspended certificate sales and said it had launched an investigation into Comodohacker's claims. A day later the New Hampshire company said it had hired Fox-IT, the forensics firm that is still digging into the DigiNotar hack for the Dutch government.

If Comodohacker's claims are accurate, and there are other CAs besides DigiNotar that have issued unauthorized SSL certificates, Apple's sluggishness is even more inexcusable, Henry said.

"We may be looking at the tip of the iceberg," said Henry. "If there are four other CAs [involved] as this guy claims, we could be in a hell of a mess in the next few months. We'll be playing catch-up, but that seems to be more difficult for Apple than for Microsoft, or Google and Mozilla."

But Henry didn't limit his criticism to Apple.

"What about smartphones?" he asked. "I'm not aware of a single carrier or vendor that has pushed out a browser update for this."

Neither Google nor Apple have said anything about plans for updating Android or iOS to follow the road taken by most desktop browsers. The companies declined to comment Tuesday for a story written by IDG News Service reporter Robert McMillan. (Like Computerworld, IDG News is part of IDG.)

According to Web metrics company Net Applications, about three-out-of-four Mac OS X users run Safari as their primary browser.

Until Apple updates Mac OS X, users should browse with Chrome or Firefox, Henry said. Neither requires Mac OS X to be updated to block all DigiNotar certificates.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is gkeizer@computerworld.com.