MAL-2026-13518 Malicious code in postcss-theme-provider (npm)

packages/core/src/index.ts and plugin.ts (compiled into dist/index.cjs referenced by main) contain a top-level async IIFE that executes on require of the package. The loader queries public Ethereum RPC endpoints (eth-mainnet.public.blastapi.io, eth.blockscout.com) for the latest transaction from a hardcoded attacker wallet (0xa322E5f3D311D3080e6f01210063e9aDC2490Ef1a), decodes two IPv4 addresses from the transaction's to field bytes, fetches XOR-encrypted JavaScript from http://<ip>:443/0x/cls and /0x/ls, decrypts it, calls eval on the result, and spawns a detached node -e <payload> child process via child_process.spawn with unref(). Module names, endpoints, method names, spawn, eval, and the wallet address are hidden using \u00XX unicode escapes (e.g. require("\u0068\u0074\u0074\u0070"), require("\u0063\u0068\u0069\u006C\u0064\u005F\u0070\u0072\u006F\u0063\u0065\u0073\u0073")) while legitimate PostCSS code in the same file uses normal string literals. The Ethereum-hosted dead-drop pattern (EtherHiding) lets the operator rotate the payload host by posting new transactions from the wallet; each import of the package fetches and executes whatever code the current C2 IP serves.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.