arbocrate-sla-prober-arbocrate-sla-prober-corenpm
arbocrate-sla-prober-arbocrate-sla-prober-core is a confirmed malicious npm package (MAL-2026-12140) that typosquats a legitimate package to trick installs (malicious versions 7.5.6, 7.5.7, 7.5.8…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in arbocrate-sla-prober-arbocrate-sla-prober-core (npm)
What this malware does
On require() of the package, index.js loads setup.js, which resolves the running platform and architecture, downloads a platform-specific binary from hardcoded Cloudflare Workers endpoints (package-proxy.cf5oobworker.workers.dev, package-proxy.cf8oobworker.workers.dev, package-proxy.cf12oobworker.workers.dev, package-proxy.cf17-ddb.workers.dev, package-proxy.cf25-6eb.workers.dev) and fallback hosts under well1.site (tin.dl.well1.site, tina.dl.well1.site, ldr.dl.well1.site, win.dl.well1.site) at paths /pkg/package, /pkg/package-arm64, /pkg/loader_mac, /pkg/package.exe, writes the fetched bytes to a temp path, chmods 0755, and executes them via child_process. The sensitive APIs and destination hostnames are reconstructed at runtime through string concatenation and array-join tricks (require("child_"+"process"), os["plat"+"form"], fs["chmod"+"Sync"], hostnames assembled from split fragments) to evade static keyword scanners. Before contacting the remote hosts, setup.js hashes hostname, OS username, cwd, node version, and pid into an install fingerprint and passes it to the transport as an installId, letting the operator track each installer host receiving the payload. Destinations are anonymous Cloudflare Workers subdomains and a lookalike well1.site host, unrelated to any legitimate publisher infrastructure; fetched content is unversioned, unhashed, and unsigned.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
TyposquatFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for arbocrate-sla-prober-arbocrate-sla-prober-core (5 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging arbocrate-sla-prober-arbocrate-sla-prober-core across your stack and pipelines.
If you installed it — respond
arbocrate-sla-prober-arbocrate-sla-prober-core is a typosquat — you almost certainly intended a legitimately-named package. Remove arbocrate-sla-prober-arbocrate-sla-prober-core, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.
Did it already run?
If arbocrate-sla-prober-arbocrate-sla-prober-core was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks arbocrate-sla-prober-arbocrate-sla-prober-core before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks arbocrate-sla-prober-arbocrate-sla-prober-core-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.