secp256k1-node is a Node.js binding for an Optimized C library for EC operations on curve secp256k1. In "elliptic"-based version, "loadUncompressedPublicKey" has a check that the public key is on the curve. Prior to versions 5.0.1, 4.0.4, and 3.8.1, however, "loadCompressedPublicKey" is missing that check. That allows the attacker to use public keys on low-cardinality curves to extract enough information to fully restore the private key from as little as 11 ECDH sessions, and very cheaply on compute power. Other operations on public keys are also affected, including e.g. "publicKeyVerify()" incorrectly returning "true" on those invalid keys, and e.g. "publicKeyTweakMul()" also returning predictable outcomes allowing to restore the tweak. Versions 5.0.1, 4.0.4, and 3.8.1 contain a fix for the issue.