Adobe has updated its Reader and Acrobat products to shore up a major vulnerability that already is being exploited in the wild, the company said.

An Adobe advisory said the "critical" vulnerability, spotted in Reader and Acrobat 8.1.2 and earlier versions, is related to an unspecified JavaScript input validation issue. If exploited, the bug could permit remote code execution.

Andrew Storms, director of security operations at vendor nCircle, said on Tuesday that Adobe this year already has patched at least one other Acrobat flaw related to a JavaScript error.

"It would appear that Adobe has an epidemic with regard to JavaScript," he told SCMagazineUS.com in an email. "One begins to wonder just how many more are yet to be found. We may be witnessing an interesting twist. It appears that Microsoft Word might be on the track to be more secure, while Adobe Acrobat is going in the opposite direction."

He said the company released few details about this latest vulnerability, probably to ward off the potential for further exploits. Adobe said in its advisory that is has received reports of exploits appearing in the wild.

Jason Lam, a senior security analyst at a Canada-based financial institution and a handler for the SANS Internet Storm Center, warned of an uptick in compromised websites being used to distribute the exploit.

"This is likely to appear in a malware spreading website near you soon given the track record of the botnet operators," he wrote on the Storm Center's blog. "Suggest [you] update this one as soon as possible."

Adobe Reader and Acrobat versions 7.1.0 are not affected.

An Adobe spokesman said he was checking into the matter.