This indicates an attack attempt against a memory-corruption vulnerability in Mozilla Firefox, Thunderbird, and SeaMonkey.
This vulnerability is caused by the application's failure to properly free structures. A remote attacker may exploit this to execute arbitrary code or cause a denial-of-service condition.
Mozilla Firefox version 188.8.131.52 and prior
Mozilla Thunderbird version 184.108.40.206 and prior
Mozilla SeaMonkey version 1.0.5 and prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Denial of Service.
Upgrade the software to the latest version: