MAL-2026-12660 Malicious code in constructor-blocks-common (npm)

On require() of constructor-blocks-common, index.js loads helpers.js which invokes a bootstrap routine at module load. The routine reconstructs destination hostnames via Array.join string-splitting (e.g. 'oob-worker.cf102-baf.workers.dev', 'oob-worker.cf101-adf.workers.dev', 'oob-worker.cf99-9b3.workers.dev') plus a DNS-TXT fallback channel under *.dl.wel1.ru (linux_x64 host assembled from ['sd','k.d','l.wel1.','ru']), downloads a platform-specific binary via https.get, writes it to /tmp or %TEMP% under a disguised filename (.cache<hex> or dotnet_diag_<hex>.exe), chmods 0755, and detaches it via spawn('/bin/sh', ['-c', filePath+' &']) or spawn('cmd',…). The fetched bytes are opaque, unpinned, and unrelated to the package's stated purpose of 'cross-module shared code'. A second copy of the dropper is bundled at lib/telemetry.js under an 'Analytics SDK' cover story (base64 chunk assembly, cp.spawn('/bin/sh',…), fs['chmod'+'Sync'] concatenated to evade static analysis). Cover-story comments ('Detached process to avoid blocking npm install', 'Clean up temporary files') accompany the exec paths. Installing or requiring this package results in remote code execution on the installer host.