How to Generate Endless Attack Vectors on Web Applications

Never run out of ideas for attack vectors again.

Author

Critical Thinking Team
October 31, 2023

Introduction

When it comes to hacking web applications, one of the biggest challenges is running out of attack vectors. It can be frustrating to hit a plateau and feel like you've exhausted all possibilities. However, there are strategies and frameworks that can help you overcome this hurdle and continue finding vulnerabilities. In this article, we will explore some tips and techniques to generate endless attack vectors on web applications, based on the insights shared by Douglas Day, also known as the Archangel, and other experts in the field.

Using the Application Like a Human

One key approach to finding attack vectors is to use the application like a human, rather than solely focusing on hacking it. By stepping through the application's user interface (UI) and understanding its purpose, data, and user journeys, you can gain valuable insights. Use the application like a human.

“Essentially what I do is, I leave Burp or Caido or on or whatever I'm proxying just to keep all that traffic, but I don't use any of it, and I just step through the application, the UI, like a human.”

Rhynorater, Critical Thinking, Episode 41

Reading the Documentation and Looking for "Cannot" Statements

Reading the documentation thoroughly is an underrated but effective strategy for finding attack vectors. By paying attention to "cannot" statements, boundaries, and limitations mentioned in the documentation, you can identify potential vulnerabilities.

"You're looking for cannot statements. So X user cannot do XYZ. You're looking for boundaries that have been set up in the application... And like Douglas mentioned before, you're looking for those ‘No’s."

Rhynorater, Critical Thinking, Episode 41

Exploring Grayed-Out Areas in the Application

Another technique to uncover attack vectors is to examine the grayed-out areas in the application. These areas often contain disabled buttons or text fields that are not supposed to be modified. By enabling these elements and interacting with them, you can gain a deeper understanding of the application's flow and potentially discover vulnerabilities. Using tools like Burp Match and Replace or creating a JavaScript bookmarklet to remove disabled elements and unhide hidden elements can be a real game changer.

Identifying Information in the API Response

Looking for information in the API response that is not visible in the UI can provide valuable insights into the application's functionality. This information may indicate legacy features, hidden data, or intentional security decisions. By analyzing the API response, you can understand the application's behavior in different scenarios and potentially exploit vulnerabilities.

"So that's another cool tip - if you have particularly grayed out or censored information - maybe the Social Security number only has the last four digits, or something like that - if you can find a way to leak that, then that can violate the security boundaries and the threat model that that application has set up."

Rhynorater, Critical Thinking, Episode 41

Comparing UI Differences Between Accounts

When an application has different user accounts or tiers of access, comparing the UI differences between these accounts can lead to new attack vectors. By understanding the privileges and features available to different account types, you can identify areas to target as a less privileged user. This approach is particularly useful for role-based access control (RBAC) scenarios or vertical privilege escalation. Try emulating the client-side identification of different user types through techniques like match and replace.

Bypassing Paywalls

Paywalls can often be bypassed by paying for access with one account and then attempting to access the same features with another account. Many times, the paywall is only a front-end restriction, and the functionality is already present in the back-end. By exploring these paywalls and understanding how they are implemented, you can potentially find vulnerabilities and gain access to premium features without paying. Don’t shy away from investing a small amount of money to potentially uncover high-value vulnerabilities.

Putting It All Together

By employing these strategies and techniques, hackers can generate endless attack vectors on web applications. However, it is essential to remember to evaluate the security impact of each attack vector and consider the potential consequences for the application and its users.

In conclusion, the process of finding attack vectors requires a comprehensive understanding of the application, its documentation, and its API responses. By using the application like a human, reading the documentation, exploring grayed-out areas, analyzing the API response, comparing UI differences between accounts, and bypassing paywalls, hackers can uncover vulnerabilities that may have been overlooked. As technology continues to evolve, it is crucial for security professionals to stay updated on the latest techniques and strategies to ensure the safety and integrity of web applications.