Recent security issue

Today I started getting notifications from several of my sites where a new user has been added with the username wpuser_awnmwnfwwel where the string after the underscore is random.

The common denominator between these sites is that they all had PublishPress Capabilities installed and all were on version 2.3 rather than 2.3.1.

Is the mysterious “security issue” fixed in 2.3.1 something that could be behind this, or was it unrelated?

Thanks

Tim