The flaw could have allowed attackers to access private conversations, channels, passwords, keys and tokens, and various functions within the app
One-fifth of HackerOne's hackers are full-time bounty hunters - while for others, it's a route into lucrative new IT roles
The platform has awarded $21 million to hackers in the year for finding and reporting security bugs
The vulnerability was reported to Valve Software but was rejected for being 'out of scope'
HackerOne research reveals the biggest winners from more than 120,000 security vulnerabilities reported by hackers on 1,400 programmes
Google increases rewards to $5,000 for identifying remote-code execution flaws in Android apps