This indicates an attack attempt to exploit a Remote Code Execution vulnerability in Joomla!
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application when handling crafted HTTP headers. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted HTTP header.
Joomla! CMS versions 1.5.0 through 3.4.5
System Compromise: Remote attackers can gain control of vulnerable systems.
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