Approximately 200,000 websites running WordPress have been affected by a malware attack from a plug-in that installed a backdoor, allowing a malicious actor to publish spam, collect IP addresses and more.

Wordfence, a security firm that focuses on the popular content management system, said in a blog post that the malware attack has been traced to a plug-in called Display Widgets, which was purportedly designed to manage the way other plug-ins are displayed on WordPress sites. Though it has recently been removed, the threat actor behind the malicious activity did not give up easily.

According to SecurityWeek, the original creator of Display Widgets sold it in late June, after which it was almost immediately updated with a backdoor. David Law, a freelance SEO consultant, noticed the initial malware attack and informed Wordfence, which removed it from the WordPress plug-in repository.

Just a few days later, however, Display Widgets emerged again, this time with an additional file called geolocation.php that could perform the same kind of malware attack, Bleeping Computer reported. When site owners looked at their WordPress admin panels, though, the malicious content was invisible; again, Law detected the malicious activity by tracking visits to an external server by the plug-in.

History then seemed to repeat itself in July and even earlier this month, an article on SC Magazine said, with the Display Widgets owner even making it obvious that the plug-in was being refined to continue launching the same kind of malware attack. In total, the plug-in was made available at least four times before it was pulled for good.

Law has since published his own account of the Display Widgets story. In the post, he provided an overview of the various versions involved and suggested deleting the plug-in. WordPress, meanwhile, banned the developer from its platform following the malware attack and issued critical alerts each time Display Widgets was removed.

Though the extent of the damage may have been limited to spamming various websites, the story illustrates how persistent cybercriminals can be, even in the face of repeated retaliatory action by companies the size of WordPress. It’s also a cautionary tale about the relative ease with which plug-ins can be bought, sold and repurposed for uses the original creators probably never would have imagined.