1. Web Security Academy
  2. Client-side prototype pollution
  3. Preventing
  4. Lab

Lab: Client-side prototype pollution via flawed sanitization

PRACTITIONER

This lab is vulnerable to DOM XSS via client-side prototype pollution. Although the developers have implemented measures to prevent prototype pollution, these can be easily bypassed.

To solve the lab:

  1. Find a source that you can use to add arbitrary properties to the global Object.prototype.

  2. Identify a gadget property that allows you to execute arbitrary JavaScript.

  3. Combine these to call alert().

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