Contestants in a high-stakes hacking contest had no trouble toppling the Apple Safari and Microsoft Internet Explorer browsers, proving for a fifth year in a row that no software or application is safe from people with the expertise and motivation to exploit them.

The attacks came on Day One of the Pwn2Own contest, which pays more than $15,000 apiece for exploits that successfully give the attacker full remote access of the targeted machine. Wednesday's event saw hackers take complete control of a fully patched Sony Vaio and MacBook Air by compromising IE and Safari respectively. Google's Chrome browser was also up for grabs, but no one stepped forward to try hacking it.

“Every browser, every operating system, has its own vulnerabilities,” said Chaouki Bekrar, CEO of Vupen Security and the contestant who successfully hacked Safari. “This is what we wanted to demonstrate – that we can create a very reliable exploit for Apple Mac OS and Safari without even crashing the browser.”

Contest rules forbid him from disclosing most technical details behind the vulnerability, but he was permitted to say that it involved what's known as a use-after-free flaw in the Apple browser. He said the exploit used a technique known as return-oriented programming to bypass a security protection known as data execution prevention that is built into many Apple programs.

The hardest part of the exercise was writing fuzzing, debugging, and memory dumping software for Macs.

“On windows, you have everything available on the internet,” he said. “You can download everything you want. In (OS X) there is not even shell code available on the internet.”

After building the tools from scratch, it took him about two weeks to find the bug and set out to exploit it. The result was an attack that reliably commandeers a Mac when Safari visits a website that hosts the malicious code.

“Just after visiting the webpage with the affected version of Safari, we can, for example, launch the calculator or open a shell or do anything else we want,” he said a minute or two after demonstrating the exploit at the contest, which was attended by members of Apple's security team. “We have the same privileges as the user who visited the webpage.”

He said users would have no way of knowing their machines have been compromised. There is no prompt asking for a password. The only way to thwart the attack is to run Safari from an account that has been configured to have limited privileges.

Under competition rules, contestants drew a lottery to determine who was the first to attempt hacking a particular browser. Once a browser was compromised, it was eliminated from the running. Both IE and Safari were hacked on the first try.

“I have an exploit all ready to go, and now it's just sitting in my bag,” said Charlie Miller, a three-time Pwn2Own winner, shortly after Bekrar took this year's prize. “You'd think Apple would be concerned about it.”

Miller said he's had the working attack for more than nine months now. Even after Apple patched a whopping 62 Safari security bugs just hours before the contest started, Miller's exploit still worked, he said.