As many as 47,337 malicious plugins have been uncovered on 24,931 unique websites, out of which 3,685 plugins were sold on legitimate marketplaces, netting the attackers $41,500 in illegal revenues.
The findings come from a new tool called YODA that aims to detect rogue WordPress plugins and track down their origin, according to an 8-year-long study conducted by a group of researchers from the Georgia Institute of Technology.
"Attackers impersonated benign plugin authors and spread malware by distributing pirated plugins," the researchers said in a new paper titled "Mistrust Plugins You Must."
"The number of malicious plugins on websites has steadily increased over the years, and malicious activity peaked in March 2020. Shockingly, 94% of the malicious plugins installed over those 8 years are still active today."
The large-scale research entailed analyzing WordPress plugins installed in 410,122 unique web servers dating all the way back to 2012, finding that plugins that cost a total of $834,000 were infected post-deployment by threat actors.
YODA can be integrated directly into a website and a web server hosting provider, or deployed by a plugin marketplace. In addition to detecting hidden and malware-rigged add-ons, the framework can also be used to identify a plugin's provenance and its ownership.
It achieves this by performing an analysis of the server-side code files and the associated metadata (e.g., comments) to detect the plugins, followed by carrying out a syntactic and semantic analysis to flag malicious behavior.
The semantic model accounts for a wide range of red flags, including web shells, function to insert new posts, password-protected execution of injected code, spam, code obfuscation, blackout SEO, malware downloaders, malvertising, and cryptocurrency miners.
Some of the other noteworthy findings are as follows -
- 3,452 plugins available in legitimate plugin marketplaces facilitated spam injection
- 40,533 plugins were infected post-deployment across 18,034 websites
- Nulled plugins — WordPress plugins or themes that have been tampered to download malicious code on the servers — accounted for 8,525 of the total malicious add-ons, with roughly 75% of the pirated plugins cheating developers out of $228,000 in revenues
"Using YODA, website owners and hosting providers can identify malicious plugins on the web server; plugin developers and marketplaces can vet their plugins before distribution," the researchers pointed out.