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Animal Viewer

Daily AlpacaHackTopic: Client-SideReleased: Jan 22, 2026

161 solves
Web
Medium

by

hiikunz

hiikunz

🦙🐻🐈️🐕️🐘

Beginner Hint: Client-Side Challenge (AI-translated)
  • Client-side challenges target vulnerabilities caused by processing that runs in a web browser, such as JavaScript, the DOM, and CSS.
  • In this type of challenge, you are given not only the web application instance but also another instance called the Admin Bot.
  • The Admin Bot holds secrets such as the flag and automatically executes client-side behavior using a browser like Headless Chrome.
  • Client-side behavior includes actions such as visiting pages and submitting forms.
  • The goal of a client-side challenge is to exploit vulnerabilities in this browser-side behavior and steal secrets held by the client.
  • In this challenge, the Admin Bot sets the flag in a cookie and can visit an arbitrary page.
  • Another common stumbling point is the URL format you pass to the Admin Bot.
  • The Admin Bot uses animal-viewer as the cookie domain, and due to how Docker Compose networking works, it can access the web application at http://animal-viewer:3000.
  • Therefore, the URL you submit to the Admin Bot must be http://animal-viewer:3000, which matches the cookie domain, rather than the IP address shown in the challenge statement.
animal-viewer.tar.gz

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