MAL-2026-12756 Malicious code in devplatform-spa-devtools (npm)

On require('devplatform-spa-devtools'), index.js loads runtime.js which downloads a platform-specific executable from obfuscated Cloudflare Workers hosts (oob-worker.cf103-070.workers.dev, oob-worker.cf99-9b3.workers.dev, oob-worker.cf101-adf.workers.dev) whose hostnames are reassembled from split string arrays at runtime. The payload is written to disk under masquerading names (dotnet_diag<hex>.exe on Windows,.cache_<hex> on Unix), chmod'd 0755, and spawned detached via cp.spawn('/bin/sh', ['-c', fp + ' &'], {detached:true,stdio:'ignore'}).unref() with no hash or signature verification. A fallback path uses DNS TXT record lookups against *.dl.wel1.ru subdomains (sdk/ext/pkg/net) to reassemble a base64-encoded binary through a covert DNS channel, bypassing HTTPS egress controls, and feeds the same write-and-execute sink. Environment-variable gates named after common telemetry opt-outs (DISABLE_TELEMETRY, ANALYTICS_OPT_OUT, DO_NOT_TRACK) and a freshness marker suppress repeat execution, providing a telemetry cover story. The workers.dev subdomains and the wel1.ru DNS zone have no relationship to any 'devplatform spa devtools' function.