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exploiting-jwt-algorithm-confusion-attack

95 / 100 · Low risk

Fine to try.

By plurigrid/asi (GitHub) · other · 72 stars · scanned at commit 293ce9f

Exploits JWT algorithm confusion vulnerabilities where the server's token verification library accepts the algorithm specified in the JWT header rather than enforcing a fixed algorithm. The tester manipulates the alg header to switch from RS256 to HS256 (using the RSA public key as the HMAC secret), sets alg to none to bypass signature verification, or exploits kid/jku/x5u header injection to supply attacker-controlled keys. Activates for requests involving JWT algorithm confusion, alg none att…

Works with any agent that supports SKILL.md skills.

What this skill can do

Install

Paste this into your terminal. It downloads exactly the version we scanned, not whatever is newest.

if [ -e ~/.agents/skills/'exploiting-jwt-algorithm-confusion-attack' ] || [ -L ~/.agents/skills/'exploiting-jwt-algorithm-confusion-attack' ]; then echo 'A skill folder named exploiting-jwt-algorithm-confusion-attack already exists — not replacing it' >&2; false; else d=$(mktemp -d) && git clone --quiet --filter=blob:none --no-checkout 'https://github.com/plurigrid/asi' "$d" && git -C "$d" checkout --quiet '293ce9f76e3abcd5ba18db284688bc0d9ac6691d' -- 'plugins/asi/skills/exploiting-jwt-algorithm-confusion-attack' && mkdir -p ~/.agents/skills && cp -R "$d"/'plugins/asi/skills/exploiting-jwt-algorithm-confusion-attack' ~/.agents/skills/'exploiting-jwt-algorithm-confusion-attack' && rm -rf "$d"; fi

Codex reads ~/.agents/skills directly. For Claude Code, Cursor, Copilot, Gemini CLI, Antigravity or OpenCode, also link it. For Claude Code: ln -s ~/.agents/skills/'exploiting-jwt-algorithm-confusion-attack' ~/.claude/skills/'exploiting-jwt-algorithm-confusion-attack' (other agents: ~/.cursor/skills, ~/.copilot/skills, ~/.gemini/skills, ~/.gemini/config/skills, ~/.config/opencode/skills). Or install through the finder skill, which does both.

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