Wordfence on "[Plugin: Wordfence Security] Modified plugin file: wp-content/plugins/.../readme.txt"

OK found it. He/she checked in code into the 5.5.2 tag after the release:

https://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&new=826766%40events-manager&old=794571%40events-manager&sfp_email=&sfph_mail=

So what I would do if I were you (and anyone else suffering from a plugin developer who checks code into their tags) just do a repair on files which have changed. This will have the same effect as if you were to uninstall the plugin and reinstall the newer version 5.5.2 while retaining any settings or data that might be removed on uninstall.

Sound good?