2026weight 24.24Hack for a Change

Hack for a Change 2026 March: UN SDG 3

3 challenges with 3 published community solutions between them. Solution links go to CTFtime’s task page, which aggregates every writeup for a challenge - individual blog posts rot, the aggregator does not.

Full task list on CTFtime

Cryptography1

Recover a plaintext or a key from something that was supposed to protect it. In practice: identify the scheme, find the parameter the author got wrong, exploit it.

Solve it with:Cipher identifier and automatic decoder Vigenere cipher solver with automatic key recovery RSA decryption and attack runner Wiener’s attack on small RSA private exponents In-browser hash cracker with rule transforms Learn: Classical ciphers and frequency analysis Learn: RSA and the parameters that break it

Genome LCG Oracle
1 pts1 writeup
Same technique in picoCTF: StegoRSA, Timestamped Secrets, AES-ABC

Web1

Reach data or functionality the application meant to keep from you - through its inputs, its tokens, or its trust in the client.

Solve it with:JWT decoder and signature verifier JWT alg=none bypass generator Web attack payload catalog JWT secret brute force Learn: Web attacks and session tokens

Clinical Gateway SSRF
1 pts1 writeup
Same technique in picoCTF: Client-side-again, dont-use-client-side, Irish-Name-Repo 3

Misc1

Everything that fits no other box: esolangs, puzzles, scripting exercises, and the jail escapes that have not yet earned their own category.

Solve it with:Brainfuck and esolang decoder Cipher identifier and automatic decoder Regex tester with match offsets and capture groups Learn: Recognising encodings

Prescription Pad
1 pts1 writeup
Same technique in picoCTF: Permissions, Specialer, Codebook

Cryptography1

Genome LCG Oracle

Web1

Clinical Gateway SSRF

Misc1

Prescription Pad

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