Security Experts:

XSS Flaw in YouTube Gaming Earns Researcher $3,000

Google has paid out a $3,133.7 bounty to a researcher who identified a cross-site scripting (XSS) vulnerability on the recently launched YouTube Gaming website.

YouTube Gaming, quietly launched by YouTube in late August, provides both live-streamed and on-demand gaming videos. The new service competes with Amazon-owned video game streaming website Twitch.

Ashar Javed, a penetration tester with Hyundai AutoEver Europe whose name is in the security hall of fame of several major companies, claims it only took him two minutes to find a reflected XSS vulnerability in YouTube Gaming’s main search bar.

According to the researcher, the website validates user input to prevent injection of potentially malicious code, but developers failed to escape the “</” string, allowing an attacker to use a payload like </script><script>confirm(document.domain)</script>.

As with all reflected XSS flaws, the attacker needed to trick the victim into clicking on a specially crafted link in order for the attack to work. If successful, the exploit could have been used to access cookies, session tokens and other sensitive information stored in the victim’s browser, and inject arbitrary content into the web page, which can be highly useful for phishing attacks.

The vulnerability was reported to Google on October 22 and it was fixed within a week, Javed told SecurityWeek. The Internet giant awarded the expert $3,133.7 for his work.

According to Javed, it’s common for developers to omit the “</” string when sanitizing user input. The bug bounty hunter says he has identified similar XSS vulnerabilities in Netflix, the Russian search engine Yandex, and at least ten other popular websites.

Additional technical details on how Javed identified the XSS vulnerability in YouTube Gaming are available on the researcher’s blog.

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Related Reading: Web Application Firewalls Tested Against XSS Attacks

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.