In a post published Thursday, Jetpack researcher Harald Eilertsen said timestamps and other evidence suggested the backdoors were introduced intentionally in a coordinated action after the themes and plugins were released. The affected software was available by download directly from the AccessPress Themes site. The same themes and plugins mirrored on WordPress.org, the official developer site for the WordPress project, remained clean. “Users who used software obtained directly from the AccessPress website unknowingly provided attackers with backdoor access, resulting in an unknown number of compromised websites,” Ben Martin, a researcher with Web security firm Sucuri, wrote in a separate analysis of the backdoor.
The Jetpack post said evidence indicates that the supply chain attack on AccessPress Themes was performed in September. Martin, however, said evidence suggests the backdoor itself is much older than that. Some of the infected websites had spam payloads dating back nearly three years. He said his best guess is that the people behind the backdoor were selling access to infected sites to people pushing web spam and malware. He wrote, “[…] it seems that the malware that we’ve found associated with this backdoor is more of the same: spam, and redirects to malware and scam sites.” The Jetpack post provides full names and versions of the infected AccessPress software. Anyone running a WordPress site with this company’s offerings should carefully inspect their systems to ensure they’re not running a backdoored instance. Site owners may also want to consider installing a website firewall, many of which would have prevented the backdoor from working.
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