A vulnerability has been discovered in the Opera web browser that could be exploited by hackers to run code on a user's system. 

Security website Secunia rated the flaw as highly critical. 

The problem is caused by an integer overflow when the browser processes JPEG images, and could be activated using a specially crafted JPEG image.

If excessively large height and width values are specified in certain fields of a JPEG file, Opera allocates insufficient memory for the image.

This leads to a buffer overflow when the image is loaded into memory, which can be exploited to execute arbitrary code.

The problem was first reported by security management firm VigilantMinds. 

The flaw is known to affect version 8.54 of the Opera browser and may also be found in prior versions. The problem can be resolved by upgrading to Opera 9.

"Additionally, users should exercise caution while accessing the web, and should do so from accounts with limited privileges," said a statement from VigilantMinds.