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Daily AlpacaHack

A CTF challenge series with fun puzzles to enjoy every day

What is Daily AlpacaHack?

We regularly publish simple, beginner-friendly or educational CTF challenges!

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Solve each challenge within its time window to appear on the leaderboard.

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Today's Challenge
tchentchen
List Sharing
Web
Medium
44 solves
Submissions (latest 3)
despair09

SOLVED!

Aug 16, 6:32 PM

Leaderboard

Try the first challenge

Is this your first CTF? Let's begin by tackling the first challenge released on Daily AlpacaHack.

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admin
AlpacaHack 2100
Misc
Welcome🌱
2,125 solves
Upcoming challenges reveal the , , and in advance.
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Aug 2026

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27
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Welcome🌱
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tchentchen
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tchentchen
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tchentchen
List Sharing
Web
Medium
44 solves
18-20
tan90909090tan90909090
Planned topicObfuscation
Rev
Hard
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Planned topicPython
Web
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24-26
Planned topicXSS
Web
Hard
27
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Writeups

Writeup for Ruby Flag Checker

haruhana

ja
Ruby Flag Checker

16 hours ago

power

Writeup for Read Assembly

ja

2026/08/14 05:59

Writeup for Fermat's Last Theorem

author
ja

2026/08/13 13:59

Rows:

Leaked Flag Checker

Topic: C, Flag CheckerReleased: Dec 4, 2025

677 solves
Rev
Easy🌱2.0

by

minaminao

minaminao

flag checker everyone loves

Beginner Hint
  • This challenge is in the Rev (Reverse Engineering) category.
  • Flag checkers are a common theme in Rev problems.
  • A flag checker executable or script accepts player input and tells you whether it matches the flag.
  • The provided files are the C source challenge.c and its Ubuntu 24.04 binary build challenge.
  • In challenge.c, the flag-related string xor_flag has been edited out and hidden.
  • The goal is to use challenge.c as a reference and find an input (the flag) that makes the challenge binary print Correct.
  • Typically Rev problems don't include source code. You usually analyze only the binary. This one can also be solved without the source.
leaked-flag-checker.tar.gz

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