Backslash Powered Scanning: Implementing Human Intuition

Existing web scanners search for server-side injection vulnerabilities by throwing a canned list of technology-specific payloads at a target and looking for signatures – almost like an anti-virus. In November I released an open-source scanner that takes an alternative approach, capable of finding and confirming both known and unknown classes of injection vulnerabilities. Evolved from classic manual techniques, this approach reaps many associated benefits including casual WAF evasion, a tiny network footprint, and flexibility in the face of input filtering.

In this presentation, I’ll share with you key insights from the conception of this scanner, through development, to unleashing it on several thousand websites. Then I’ll go further and explore the offensive depth this scanner can reach, unveiling previously unseen salvos capable of automatically escalating middling vulnerabilities like HPP and JSON injection to RCE. As you might expect from a scanner designed to find high-hanging fruit, the issues it spots aren’t always easy to comprehend or exploit. I’ll show how to handle its most confounding and entertaining findings, leaving you equipped to deploy it to maximum effect, and adapt and refine it to complement your testing.

James Kettle

James Kettle is Head of Research at PortSwigger Web Security, where he designs and refines vulnerability detection techniques for Burp Suite’s scanner. Recent work has focused on techniques to detect unknown classes of vulnerabilities, and exploiting subtle CORS misconfigurations in bitcoin exchanges. James has extensive experience cultivating novel attack techniques, including server-side RCE via Template Injection, client-side RCE via malicious formulas in CSV exports, and abusing the HTTP Host header to poison password reset emails and server-side caches. He has spoken at numerous prestigious venues including both BlackHat USA and EU, and OWASP AppSec USA and EU.