Veeam Explorer for Microsoft Exchange Javascript Execution Vulnerability
When using the Veeam Explorer for Exchange in Backup & Replication or backup for Office365, and doing a preview of a message, and the item contains HTML, and has javascript into it, the embedded script may be executed.
Veeam has released a private hotfix for this.
See the Veeam KB here: https://www.veeam.com/kb2847