This indicates an attack attempt to exploit a Memory Corruption vulnerability in Opera.
The vulnerability is due to a heap buffer underflow when the vulnerable software handles a maliciously crafted GIF file. An attacker can exploit this by tricking an unsuspecting user into opening a malicious GIF file and execute arbitrary code within the context of the application.
Opera Software Opera 12.11 and earlier versions
System Compromise: Remote attackers can execute arbitrary code within the context of the target user's browser.
Currently we are unaware of any vendor supplied patch or updates available for this issue.