This indicates an attack attempt to exploit an Information Disclosure vulnerability in WebNMS Framework.
The vulnerability is caused by improper validation of user supplied data when the vulnerable application handles a maliciously crafted request. An attacker can exploit this to impersonate any users and obtain their authenticated session cookies.
WebNMS Framework 5.2 and 5.2 SP1
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems
Apply the most recent upgrade or patch from the vendor