On Jan 1, 2016 version 4.7 of this add-on was released to address an exploitable SQL injection vulnerability. If you are still using a version of this add-on which is below 4.7 or released before Jan 1, 2016 then it is essential that you update to the latest version of the add-on as soon as possible to fix this security issue.
Similar Threads v5.3 changes:
Fixed bug in code dealing with Create Thread.
Similar Threads v5.1 changes:
Fixed problem where Exclude Forums field in the Options page had nothing selected and would cause a server error.
Similar Threads v4.5 changes:
Fixed the Exclude Days for those using the Standard Search.