MyBB 1.8.15 has been released and it does contain a huge number of security fixes. 10 low and medium security vulnerabilities have been addressed with the .15 release.
24 other issues have been resolved, including important permission issues with the delayed moderation feature.
You should update your forum to 1.8.15 as soon as possible. If you can not update soon, check your moderators permissions and remove the delayed moderation permission to be safe.
Note that the update script is required for the 1.8.15 update.