Hi Folks, Today, I'm gonna share one of my interesting finding in bug bounty. I occasionally hunt bugs in bug bounty in my free time. So, I don't have enough time to blog. But on someone request, I share some of my bug bounty findings here. I like to find some interesting and logical bugs. Recently, I found an interesting bug in many sites but I can't disclose the name of every website, one website 'Upwork' already patched this bug and resolved the report that's why I disclose the name. So, what's the bug?   Denial of Service (DoS) > Single user cookie based DoS There are a lot of websites using WAF like Cloudflare etc. When the Cookie sets with malicious characters(like"><script> alert(1)</script> mean  with XSS or SQLI payloads etc.) value, the site WAF like Cloudflare block us from accessing that website, we need to remove that cookie to access the site Many websites sets 'Referrer'