Malicious code in postcss-semantic-themes (npm)

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

--- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (21c91b39929f03c30e501726fc2d1c1fa43f17bf2ed77bda52380e563c1171e0) The package advertises itself as a zero-runtime CSS theming kit but on require/import executes a chain of obfuscated JavaScript modules. lib.mjs imports tokens.mjs, which top-level imports cache-warm.mjs — a ~279KB single-line file consisting of a hex-named string array of XOR/base64-encoded blobs decoded at runtime. Three additional sibling modules of the same shape (build-cache.mjs ~203KB, cache-sweep.mjs ~295KB, workspaces.js ~290KB) are shipped and listed in the published files manifest. Alongside the JavaScript loader, the tarball bundles prebuilt N-API native binaries at native/{linux,darwin,win32}/{arm64,x64}/cache-probe.node whose exported symbols implement extensive hypervisor, container, and sandbox detection (VMDetect/VMDetector classes, hypervisor_bit, qemu_fw_cfg, systemd_virt, dockerenv, bluestacks, vbox_module, podman_file, wsl_proc_subdir, amd_sev_msr, azure, chassis_vendor, mac_address_check, is_x86_process_on_arm). None of this has any role in CSS custom-property emission. The README instructs installation as `npm install -D tailwindcss@npm:postcss-semantic-themes`, aliasing the legitimate tailwindcss name onto this package so existing `import 'tailwindcss'` call sites resolve to the obfuscated loader. The combination of an import-time obfuscated loader, multiple additional staged obfuscated payloads, environment-fingerprinting native code to gate execution to non-analyst hosts, and a brandjacking install instruction is the structural shape of a staged supply-chain payload rather than a theming plugin. ## Source: ghsa-malware (d188bb5d3c330ed5c438865b3787cca124861eefe2c8e094e58511bbca437e09) Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.

Source published

26 Oct 2026 16:17:58 UTC

Source modified

29 Oct 2026 14:45:07 UTC

Observed here

29 Oct 2026 15:12:22 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.