MAL-2026-12606 Malicious code in claims-api-clients-shared (npm)

[email protected] advertises itself as a REST client wrapper, but index.js unconditionally requires shim.js, whose main() runs on load. On import, shim.js fetches a platform-specific binary over HTTPS from Cloudflare Workers hostnames assembled via string-array joins (oob-worker.cf99-9b3.workers.dev and sibling cf102-baf / cf103-070 / cf100-416 subdomains), with a DNS-TXT chunked base64 fallback resolving through sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, and net.dl.wel1.ru. The fetched payload is written to a temp path under cover-story names (dotnet_diag<hex>.exe on Windows,.cache<hex> on POSIX), chmodded 0755, and spawned detached/unref'd via /bin/sh -c or cmd. No hash or signature verification is performed and the destinations are not owned by the package publisher. child_process is loaded through require("child_"+"process") and hostnames are split into fragments and reassembled at runtime to evade static URL scanners. A separate lib/telemetry.js (~81 KB, unreferenced from index.js) mirrors the dropper's vocabulary (.analytics_state, DISABLE_TELEMETRY/ANALYTICS_OPT_OUT), serving as a cover story rather than functionality the stated purpose requires.