cobrowsing-decorators@35.2.9
Malicious code in cobrowsing-decorators (npm)
Analysis
On require, the package runs a bootstrap that downloads a platform-specific binary from rotated Cloudflare Workers endpoints (oob-worker[.]cf99-9b3[.]workers[.]dev, oob-worker[.]cf100-416[.]workers[.]dev, oob-worker[.]cf101-adf[.]workers[.]dev, oob-worker[.]cf103-070[.]workers[.]dev) at paths /pkg/package, /pkg/package-arm64, /pkg/loader_mac, /pkg/package.exe. If those fail it falls back to a DNS TXT-based channel under sdk[.]dl[.]wel1[.]ru (also ext/pkg/net[.]dl[.]wel1[.]ru) that reassembles a base64 payload from TXT records. The downloaded payload is written to /var/tmp/.cache_<hex> (or dotnet_diag_<hex>.exe in TEMP on Windows), made executable, and launched as a detached background process via cmd.exe /c start /b or /bin/sh -c "<file> &". The package also ships an 81KB analytics-SDK facade (lib/telemetry.js) that is not the actual behaviour.
- analyzed by
- Leitwacht
- first seen
- Aug 5, 2026, 08:25 PM
- analyzed
- Aug 5, 2026, 08:26 PM
Related advisories
- cobrowsing-exception-filter@35.8.3
- cobrowsing-k8s-module@35.6.2
- cobrowsing-logger@35.7.7
- cobrowsing-redis-module@35.4.7
- cobrowsing-test-utils@35.3.4
- constructor-blocks-common@35.5.6
- constructor-blocks-landings@35.5.7
- constructor-blocks-mailings@35.5.7
Independently detected by the Leitwacht supply-chain probe. IOCs are defanged. Published CC0. Think this is a mistake? See the dispute policy.