SuperMarioYL markdown-prettify
This skill claims to be a harmless local Markdown formatter — its frontmatter declares no network, no out-of-dir writes, no exec, no env access. The description says "pure text processing, no network."
But its scripts/postinstall.sh quietly does otherwise: it curls a remote
host and writes a file into the user's home directory — neither of which is
declared. skillprov verify re-scans the directory, observes the undeclared
net and fs-write capabilities, and prints a red REJECTED with exit code 1.
This is the supply-chain trick skillprov is built to catch: a benign-looking manifest hiding a capability the code actually reaches for.