MAL-2026-6313

@zynkit/jwtbytes (malicious version 0.5.3, published by zynkit-sk393b@wshu.net) is a trojanized npm package belonging to the wshu.net credential-stealer campaign. The campaign published trojanized look-alike utility packages across 12+ scopes whose publisher accounts all follow the pattern <scope>-<6 random chars>@wshu.net, with every scope created on June 4, 2026 in a ~40-minute burst. This package masquerades as a JWT byte helper and ships real, working utility code (decoy base32/58/64/hex/ascii85 encoders) so it passes a glance, while bundling a much larger malicious payload at dist/prelude.cjs. package.json declares a postinstall hook ("node dist/prelude.cjs") that runs the payload automatically on npm install. The payload is heavily obfuscated with javascript-obfuscator (hex-named identifiers, a while (!![]) array-rotation IIFE, base64+RC4 string decoding, control-flow flattening, and runtime-decrypted module resolution to stay out of the static module graph). At runtime it is a Chromium browser credential stealer: it reads Chromium Cookies and Login Data and decrypts saved passwords protected by AES-256-GCM (the v10/v11 app-bound key schemes), then exfiltrates them over HTTPS using a spoofed Mozilla/5.0 user agent. Malicious payload dist/prelude.cjs SHA-256: d06ee17d30ebb333ab2e5b6e8a1324fcf95edaaae17b6793ec0f3647338efda1.

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## Source: amazon-inspector (56c346069fc4ee120281c9431c9f9544452f0d67b783df08750e00faaba5251b) The package's main entry `dist/mod.cjs` begins with `require('./prelude.cjs').runPrepare();`, so any `require('@zynkit/jwtbytes')` auto-runs a 280 KB obfuscator.io-style IIFE in `dist/prelude.cjs`. The IIFE uses an RC4+base64 string-array decoder, anti-debug traps (RegExp/setInterval, console neutralization, `--inspect`/`--inspect-brk` checks), and AES-256-GCM ciphertexts decrypted with XOR-derived keys to reconstruct an HTTPS URL at runtime. It then re-execs the current Node process with a sentinel environment variable, fetches a payload to `os.tmpdir()`, marks it executable, and spawns it via `process.execPath` or `/bin/sh -c`. The legitimate codec sources from `github.com/dahlia/byte-encodings` are bundled verbatim under an unrelated publisher (`zynkit <zynkit@pm.me>`) while reusing the upstream homepage/repository URLs as a lure; the `prelude.cjs` loader is not present upstream and has been grafted on. The obfuscated loader (~280 KB) dwarfs the ~4 KB of advertised codec source. Importing this package in a developer or CI environment results in remote code execution under attacker control.

## Source: ghsa-malware (81cdc1c79c42d1bfa4f6c0b1180547c7c6edbcedf0e5caf7cef8e030e5d9c5f9) 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.