@workoscalif/sudokunpm
Advisory published Updated
@workoscalif/sudoku is a confirmed malicious npm package (MAL-2026-13366) that executes malicious code on install (malicious versions 1.2.0, 1.3.0, 1.4.0…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in @workoscalif/sudoku (npm)
What this malware does
package.json declares a postinstall script that spawns vendor/gridgen-linux-x64 during npm install. The README describes this file as a ~34 kB static ELF built from a ~150-line C sudoku generator (native/gridgen.c), but the shipped artifact is a ~33.6 MB Go runtime executable (strings include runtime., reflect., GODEBUG, chacha8, godebugs.Info) — roughly 1000x the advertised size and a different language/toolchain than the shipped source. The binary contains /proc/self/cgroup and /proc/self/mountinfo strings, which are container/CI environment fingerprints unrelated to generating sudoku puzzles. The postinstall short-circuits unless process.platform === 'linux' && process.arch === 'x64' and honors SUDOKU_SKIP_POSTINSTALL=1, so developer laptops (macOS/Windows) and reviewers using --ignore-scripts do not execute the binary. The npm scope @workoscalif visually resembles the WorkOS authentication vendor while the package is an unrelated personal project (author anas cherni, homepage github.com/anascherni/sudoku), increasing the likelihood a developer installs it believing it is vendor-endorsed. The combination of a documentation/contents mismatch, a large opaque binary from an unrelated toolchain, Linux-x64/CI gating, container fingerprinting strings, and a scope resembling a known vendor is the opaque-native-binary dropper shape rather than the advertised C sudoku helper.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Malicious packageFind it
Search your lockfiles and build artifacts for @workoscalif/sudoku (6 malicious versions).
If you installed it — respond
Remove @workoscalif/sudoku from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.
Did it already run?
If @workoscalif/sudoku 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 @workoscalif/sudoku-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.