The owner of iPhone developer website iPhoneDevSDK says his team has patched a security hole behind malware that infected employee computers at Facebook, making the developer site safe to visit again.

"It is clean now," said Ian Sefferman, iPhoneDevSDK's owner and operator, in an email to The Verge. Sefferman and his colleagues are still trying to figure out exactly what went wrong and how to keep their site and its 200,000 registered users secure from hackers in the future. Malware found on employee computers at Apple and Twitter also may have come from the site while it was compromised.

"In the short term, we've reset all user passwords just in case (though we don't have any evidence that user data was compromised)," Sefferman wrote. "We're still investigating the root cause and proper fix to ensure we aren't compromised again going forward."

On February 15th, Facebook disclosed that it was targeted in a "sophisticated attack" which it had contained, and pointed the finger at an unspecified "mobile developer website" as being the source of the malware on its employee computers. Sefferman says he didn't learn about any security issues on his website until AllThingsD published an article yesterday naming iPhoneDevSDK as the website Facebook was talking about, linking it to other attacks reported by Twitter and Apple.

In a post on the iPhoneDevSDK general forums last night, excerpted by Buzzfeed, Sefferman explained the security hole had been traced back to "a single administrator account." Attackers commandeered the admin account and used it to edit the website's code and insert a previously unseen JavaScript exploit, which targeted certain visitors. Sefferman also wrote that iPhoneDevSDK was working with Facebook's security team and law enforcement on an investigation into the attacks, adding that "as the most widely read dedicated iOS developer forum, we're targeted for attacks frequently."

But Sefferman isn't quite sure why his website was targeted for this specific attack. "We're still investigating why we were a targeted web site," he told The Verge.

Another company assisting in that investigation has been Vanilla Forums, an online community software firm that iPhoneDevSDK migrated over to in July of 2012 after suffering previous attacks.

"After doing our own investigation and collaborating with the companies that were victimized, we have concluded that the admin account in question was not compromised by a breach of Vanilla's software," said Luc Vezina, CEO of Vanilla Forums, in an email to The Verge. He continued:

"The malware was not in our servers...We take security very seriously and our application has undergone several penetration test and security audits. We are currently implementing additional account highjacking detection similar to what sites like Facebook do."

As for what prior users who have visited iPhoneDevSDK should do if they're worried about their machines, both Vezina and Sefferman recommended users update to the latest Java and OS X security patches.

There is one more thing Sefferman is sure of about the hack at this time: "This was absolutely a case of an attack from someone on the outside." Recent reports from other news outlets have speculated the attacks came from Eastern Europe, but neither Sefferman nor Vezina volunteered their own suspects.