FreeScout is a free self-hosted help desk and shared mailbox. Prior to version 1.8.181, when an administrative account is a deleting a user, there is the the possibility of a race condition occurring. This issue has been patched in version 1.8.181.
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.