Google doubled its top bounty, from $50,000 to $100,000, "for the persistent compromise of a Chromebook in guest mode."

Researchers wrote: "Since we introduced the $50,000 reward, we haven't had a successful submission.”

To qualify, the compromise, delivered via an online form (a link can be found on Google's rewards page), must remain in the device even after it has been rebooted.

The reason that they are interested in Guest mode is that guest mode allows the user to share their device without divulging personal information and is reportedly the mode when Chromebook uses its highest defensive measures.

Google has also implemented a downloading protection bypass bounty for methods that bypass Chrome's Safe Browsing download protection features. This involves flagging potentially malicious urls.

Source: SCMagazine