Security researchers have wasted no time in prodding Firefox 3 for possible security holes.

Just five hours after the browser made its public debut, the first remote code execution vulnerability was reported.

Security firm Tipping Point revealed on Wednesday that it received the report via its Zero Day Initiative service shortly after the browser was released.

Tipping Point has declined to release the name of the researcher who discovered the flaw, nor is it disclosing any further details on the vulnerability until a patch is prepared.

However, the flaw is categorised as a 'critical' vulnerability that could allow an attacker to remotely execute code on a user's computer.

Tipping Point said that it had sent the report to Mozilla and that developers were currently working on a fix for the flaw.

The security company plans to disclose further details on the nature of the vulnerability once a patch has been issued. No attacks targeting the vulnerability in the wild have been reported.

Security firms F-Secure and Secunia both recommend that users mitigate the risk by following best practices such as avoiding suspicious links and steering clear of untrusted sites.