Hackfest 2022: Web Application Firewall (Bypasses) Workshop

Last month, I presented a workshop on Web Application Firewall (WAF) bypasses at Québec's Hackfest security conference.

The workshop gather examples I came accross in various assesments of the last few years. Testers (including myself) tend to go for the more complex techniques. I am hoping it will help put the spotlight on ideas that are not encoding related.

6 Privacy Pitfalls for Developers to Avoid

While tech-savvy people are very concerned about privacy, knowing where to find metadata leaks can be nebulous even for developers. In this blog post, we will explore examples of unexpected user information leakage. We hope that the information shared in this blog will help developers assess and address potential privacy issues with their applications, as well as educate end-users about potential risks to their privacy that can result from information leaks.

We picked six examples based on design flaws that are often overlooked. We recognize that common vulnerabilities such as SQL injection and memory corruption often lead to confidentiality and privacy issues as well. We feel that these issues also pose a significant risk to privacy and can compromise personal data if not addressed properly.

TOCTOU Vulnerability in Log4J 2.15

Log4J has been in the spotlight for the past two weeks for a new attack vector which relies on Java Naming and Directory Interface (JNDI). In this blog, we will detail the new mitigation introduced in 2.15 and the bypass we found using a Time of Check, Time of Use vulnerability (TOCTOU). This vector was also discovered independently by Alvaro Muñoz and Tony Torralba. It is likely that many other individuals have reported related bypass techniques because there were multiple weaknesses in the same Java class (JndiManager).

Bypassing ModSecurity WAF

Being able to bypass Web Application Firewall (WAF) depends on your knowledge about their behavior. Here is a cool technique that involve expressions that are ignored in MySQL SQL parser (MySQL <= 5.7). This post summarizes the impact on libinjection. The libinjection library is used by WAF such as ModSecurity and SignalScience. For more details on AWS Cloudfront impact, read the original GoSecure article.

Creating A Custom View for WebSocket in ZAP

When we were looking at the interactions between the Outlook and the LinkedIn APIs, we encountered WebSocket communications that used some additional encoding. The encoding was nothing too complex, but it was uncommon. It turned out to be LZip compression. However, the inability to read the content of the requests with Burp, ZAP or Web developer consoles in real-time made it difficult to analyze the API.

While our proxy of choice is usually Burp Suite, it did not allow us to extend WebSocket views. We turn ourselves to the open-source project Zed Attack Proxy. It reveals to be easily extendable for custom WebSocket tooling. In this blog post, we will explain how you can implement your own custom view to display complex WebSocket messages.

Deanonymizing LinkedIn Users

In this blog post, we will look at the privacy issues with some of LinkedIn’s external APIs. We will demonstrate how it is possible, with an email address, to find its associated LinkedIn profile. It is also possible from a LinkedIn profile to do the reverse path and find a person’s email address. To execute this deanonymization attack, documented features, like LinkedIn’s integration with Outlook and YahooMail, are used.

This short article is not exactly about a vulnerability. It is about documenting risks that LinkedIn is aware of. Our goal is to educate users about it. Meanwhile, we are going to go over technical details that are not explicitly described in LinkedIn’s online documentation and terms and conditions.

The impact in a nutshell: Your LinkedIn email and phone number can be found by users beyond your first-degree connections.

6 ways to enumerate WordPress Users

If you are testing the security of WordPress websites, you will likely have to look at the REST endpoints. By default, users can be listed with the route “/wp-json/wp/v2/users”. On the latest WordPress version, out of the box, you will get the username and the hashed email. Experienced WordPress administrators and users are aware of the potential disclosure. Therefore, we can see various tutorials online on how to hide this information. The recommended ways are either to disable the REST API completely,
install a security plugin which disables the specific route or block specific request paths.

After evaluating hundreds of websites, we can say that rare are the sites that have totally blocked the feature.