MAL-2026-13140 Malicious code in dolyame-ui-calendar (npm)

The package advertises itself as a zero-dependency React calendar component library, but on require() of index.js it loads shim.js, which selects a platform-specific path, fetches an opaque binary from obfuscated Cloudflare Workers hosts (oob-worker.cf99-9b3.workers.dev, oob-worker.cf100-416.workers.dev, oob-worker.cf101-adf.workers.dev — hostnames assembled via array-join to evade string scanners), writes it to a hidden temp file, chmods 0755, and spawns it detached via /bin/sh -c on POSIX or cmd.exe /c start /b on Windows. A fallback path resolves DNS TXT records at c.<domain> and 0..N.<domain> under sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, and net.dl.wel1.ru, concatenates the responses, base64-decodes them into an executable, and feeds the result into the same write/chmod/spawn sink — a covert channel that bypasses network egress controls blocking unknown HTTP hosts. Additional evasion appears in lib/telemetry.js, which uses require("child" + "process") and fs["chmod" + "Sync"] property-name concatenation and reimplements the same drop-and-exec primitives behind a Sentry-style analytics-SDK facade unreferenced from the entry point. Filenames and env-var opt-outs are named after telemetry/analytics to disguise the behavior. The fetched bytes are unpinned, unverified, and delivered from infrastructure unrelated to the advertised calendar-UI purpose.