Scraping the bottom of the CORS barrel (part 1)

TL;DR ¶ In this short follow-up to my previous post, I describe why and how I’ve added support for dynamic reconfiguration of CORS middleware in jub0bs/cors. Rethinking configuration immutability ¶ Up until now, I’ve been arguing that CORS middleware should not be reconfigurable on the fly and that any change to their configuration should require...

TL;DR ¶ A few months ago, while hunting on a public bug-bounty programme, I found a nice little bug chain that involved an insecure message event listener, a shoddy JSONP endpoint, a WAF bypass, DOM-based XSS on an out-of-scope subdomain, a permissive CORS configuration, all to achieve CSRF against an in-scope asset. Read on for a deep dive about...

TL;DR ¶ In this post, I present an XSLeak technique that allows an active network attacker to observe, from an insecure Web origin, the presence or absence of some Secure cookie that may have been set by the origin’s secure counterpart. Cookies’ crumbly beginnings ¶ Netscape (Lou Montulli, more precisely) invented cookies in 1994 in order to...

My third guest post on Honeybadger’s blog, entitled Subdomain Takeover: Ignore This Vulnerability at Your Peril has just been published!

In this post, I dissect a common misconception about the SameSite cookie attribute and I explore its potential impact on Web security. TL;DR ¶ The SameSite cookie attribute is not well understood. Conflating site and origin is a common but harmful mistake. The concept of site is more difficult to apprehend than meets the eye. Some requests are...