This indicates an attack attempt to exploit an Information Disclosure vulnerability in Accellion File Transfer.
The vulnerability is caused by an error when the vulnerable software handles a specially crafted HTML file. A remote attacker can exploit this to gain unauthorized access to sensitive information.
Accellion File Transfer version FTA_9_11_200 and prior
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Please contact the vendor at the website below for updates to resolve this issue.