Researchers have discovered a critical vulnerability in MediaWiki, an open source web platform used to manage and other “Wiki” sites.

On Wednesday, Check Point Software Technologies, an Israel-based security firm, revealed that software version 1.8 and later of MediaWiki software was vulnerable to remote code execution (RCE).

The RCE bug is particularly threatening to users' online safety because an attacker can remotely exploit the vulnerability to gain control of a web server, for instance, and potentially spread malware to site visitors.

According to internet traffic rankings from Alexa, is the sixth most popular website in the world.

On Tuesday, Chris Steipp, a software security engineer at Wikimedia Foundation, posted an announcement online saying that a security update was available for MediaWiki users in light of the bug discovery.

“Your MediaWiki installation is affected by a remote code execution vulnerability if you have enabled file upload support for DjVu (natively supported by MediaWiki) or PDF files (in combination with the PdfHandler extension),” Steipp wrote. “Neither file type is enabled by default in MediaWiki installations. If you are affected, we strongly urge you to update immediately.”

Check Point notified the security team for MediaWiki about the vulnerability on Jan. 19.