cobrowsing-test-utilsnpm
Advisory published Updated
cobrowsing-test-utils is a confirmed malicious npm package (MAL-2026-12658) that executes malicious code on install (malicious version 35.3.4). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in cobrowsing-test-utils (npm)
What this malware does
[email protected] executes a full-host dropper on require(). index.js loads support.js, which on import reconstructs obfuscated hostnames from string-fragment arrays (Cloudflare Workers subdomains under workers.dev and DNS resolver domains under dl.wel1.ru), downloads a platform-specific native binary over HTTPS with a DNS TXT-record fallback, writes it to /var/tmp/.cache<hex> on Unix or %TEMP%\dotnet_diag_<hex>.exe on Windows, chmods it to 0755, and spawns it detached via /bin/sh -c or cmd. There is no version pinning, no signature or hash verification, and the fetched binary is unrelated to the package's stated 'common helpers' purpose. Cover-story identifiers such as 'analytics_state' and 'DISABLE_TELEMETRY' do not correspond to the observed behavior. A companion module lib/telemetry.js ships the same fetch/base64-decode/chmod-0755/spawn('/bin/sh','-c', path+' &') primitives under Sentry-style analytics-SDK boilerplate. Hostname obfuscation via runtime string joining (e.g., ['sdk.d','l.wel1','.r','u'].join('') and ['oob-worker.cf','...','workers','.de','v'].join('')) is a deliberate evasion of static analysis and is inconsistent with legitimate telemetry.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Malicious packageFind it
Search your lockfiles and build artifacts for cobrowsing-test-utils (version 35.3.4).
If you installed it — respond
Remove cobrowsing-test-utils from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.
Did it already run?
If cobrowsing-test-utils was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks cobrowsing-test-utils-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.