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The Wordfence Threat Intelligence team has been tracking a large-scale attack against a Remote Code Execution vulnerability in Tatsu Builder, which is tracked by CVE-2021-25094 and was publicly disclosed on March 24, 2022 by an independent security researcher. The issue is present in vulnerable versions of both the free and premium Tatsu Builder plugin. Tatsu Builder is a proprietary plugin that is not listed on the WordPress.org repository, so reliable installation counts are not available, but we estimate that the plugin has between 20,000 and 50,000 installations. Tatsu sent an urgent email notification to all of their customers on April 7th advising them to update, but we estimate that at least a quarter of remaining installations are still vulnerable.
All Wordfence users with the Wordfence Web Application Firewall active, including Wordfence free customers, are protected against attackers trying to exploit this vulnerability.
We began seeing attacks on May 10, 2022. The attacks are ongoing with the volume ramping up to a peak of 5.9 million attacks against 1.4 million sites on May 14, 2022. The attack volume has declined but the attacks are still ongoing at the time of publication.