A German computer researcher has been paid $2,500 by Mozilla as a thank you for pointing out five flaws in its browser. Michael Krax was paid $500 per bug and got a free Mozilla T-shirt.

The payments were made as part of Mozilla's 'bug bounty' programme which offers incentives for users to identify flaws in the software.

"We developed the bug bounty programme to encourage and award community members who identify unknown bugs in the software," said Chris Hofmann, director of engineering at the Mozilla Foundation.

"This programme is one of the many ways in which the Mozilla Foundation produces safe and secure software for its users."

The system was set up last year and Krax is the fifth person to receive an award. The money is paid for critical flaws found in current versions of Mozilla software, and those working in the security industry in a professional capacity are encouraged not to apply.

Mozilla released a new version of its Firefox browser last week which fixed an animated GIF flaw.