Although web application firewall (WAF) solutions are very useful to prevent common or automated attacks, most of them are based on blacklist approaches and are still far from perfect. This talk illustrates a number of creative techniques to smuggle and reshape HTTP requests using the strange behaviour of web servers and features such as request encoding or HTTP pipelining. These methods can come in handy when testing a website behind a WAF and can help penetration testers and bug bounty hunters to avoid drama and pain! Knowing these techniques is also beneficial for the defence team in order to design appropriate mitigation techniques. Additionally, it shows why developers should not solely rely on WAFs as the defence mechanism.
Finally, an open source Burp Suite extension will be introduced that can be used to assess or bypass a WAF solution using some of the techniques discussed in this talk. The plan is to keep improving this extension with the help of the http.ninja project.