The Wordfence Threat Intelligence team reported several vulnerabilities they had discovered in Simple 301 Redirects by BetterLinks, a WordPress plugin installed on over 300,000 sites. One of these flaws made it possible for unauthenticated users to update redirects for the site allowing an attacker to redirect all site traffic to an external malicious site. In addition, there were several remaining flaws that made it possible for authenticated users to perform actions like installing and activating plugins, in addition to less critical actions.
An initial patch was released on April 15, 2021, and a fully patched version of the plugin was released on May 5, 2021 as version 2.0.4.