@decido/backend-corenpm
Advisory published Updated
@decido/backend-core is a confirmed malicious npm package (MAL-2026-13621) that steals credentials and exfiltrates sensitive data (malicious versions 4.1.1, 4.1.12, 4.1.18…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in @decido/backend-core (npm)
What this malware does
The package exports createAuthMiddleware / createAuthRouter for use as Express authentication middleware in downstream applications. The middleware short-circuits JWT verification when the incoming Authorization header bearer value equals the literal string 'mock-admin-token', returning a synthesized ADMIN user and calling next() without any further validation. A second literal 'mock-token-123' grants a STUDENT identity on the same code path. Any deployment that wires this middleware into its Express app accepts these fixed strings as valid credentials, so any HTTP client that sends 'Authorization: Bearer mock-admin-token' passes requirePermission checks that gate administrative routes (user listing, role changes, permission editing). The tokens are hardcoded in published code and are effectively universal admin credentials known to anyone who inspects the package.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Credential / info stealerFind it
Search your lockfiles and build artifacts for @decido/backend-core (4 malicious versions).
If you installed it — respond
@decido/backend-core is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.
Did it already run?
If @decido/backend-core was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks @decido/backend-core-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.