The Minify HTML plugin for WordPress is vulnerable to Regular Expression Denial of Service (ReDoS) in all versions up to, and including, 2.1.10. This is due to processing user-supplied input as a regular expression. This makes it possible for unauthenticated attackers to create comments that can cause catastrophic backtracking and break pages.
https://plugins.trac.wordpress.org/changeset/3203890/minify-html-markup