Platform THCON 2026 (Toulouse Hacking Convention)
Difficulty Easy
OS OSINT
Tags Social media OSINT, leetspeak

THCON’s Socials is the kind of warm-up OSINT challenge that’s not about tooling — it’s about reading the prompt twice and noticing the CTF authors have done something cute with their social media presence. The flag is split between two posts on two platforms, with each post hiding the other half behind an ellipsis. Visit both, stitch the halves, done.

Source: Abdelkad3r/thcon-ctf-2026 · 01-socials/.

The Prompt

The SNAFU wants y’all to be well informed in the long run so you can go to our main socials (LinkedIn and Twitter) and give us a little love there (and of course find your flag!)

The challenge supplies two real links:

Solution — the split-flag trick

Both pages carry the same announcement, but each version reveals only half the flag — with a literal ... ellipsis hiding the rest. You have to visit both and concatenate the visible halves.

LinkedIn post

[THCON 2026 CTF] If you’re reading this tweet you already hold half a flag : ...r1b3} Go ahead now and create an account on https://buff.ly/nr1bTlL!

X / Twitter post

[THCON 2026 CTF] If you’re reading this tweet you already hold half a flag : THC{5uB5C... Go ahead now and create …

X/Twitter increasingly returns HTTP 402 to unauthenticated scrapers, but for OSINT pivots like this you don’t need to render the page itself — DuckDuckGo’s site:x.com ToulouseHacking "THCON 2026 CTF" search snippet leaks the visible characters of the post directly into the SERP excerpt.

Stitch the halves

LinkedIn  :          ...r1b3}
Twitter/X : THC{5uB5C...
                ─────────────
Flag      : THC{5uB5Cr1b3}

5uB5Cr1b3 is leetspeak for subscribe — exactly what the prompt is nagging you to do on their socials.

Flag

THC{5uB5Cr1b3}

Lessons learned

  1. OSINT challenges often reward visiting every linked resource. When a prompt explicitly tells you to “go to” multiple places, the puzzle is usually about combining what you find there — not picking one.

  2. Search-engine snippets are an OSINT pivot, not just a recon shortcut. When a target page is gated or rate-limiting you (Twitter’s 402, Instagram’s login wall, LinkedIn’s view limits), the SERP excerpt is often enough to recover the literal visible text without ever loading the original page.

  3. Read the flag content as a hint. Leet-encoded flags frequently spell out the intended action or theme of the challenge. Decoding the flag is sometimes the confirmation that you solved the intended path rather than stumbling into one.

References