registry / Data exfiltration / css-env-function-shim
css-env-function-shim
CSS env() function shim for legacy browsers
This report shows the evidence for css-env-function-shim@1.0.0, the only known version.
AI Security Review
scanned 19d ago · by lpm-firewall-aiInspected source establishes automatic reconnaissance and external transmission when the published registry script loads. This behavior is unrelated to a CSS environment-function shim and supports blocking for data exfiltration.
Static reason
No blocking static signals were detected.
Trigger
Loading thunderboltRegistry.js executes the payload immediately; command collection requires Node-compatible require and child_process, and transmission uses fetch.
Impact
Unconsented disclosure of host identity, system information, hosts file contents, and network configuration.
Mechanism
Encoded strings resolve to shell execution primitives and external destinations. Commands collect host information and requests transmit their output in query parameters and subdomains.
Attack narrative
When a consumer loads the registry script, its immediately invoked function decodes command execution identifiers, runs host reconnaissance commands, and sends results to external collection endpoints. It also emits beacons. The registry manifest points consumers to this executable script. The empty default entrypoint limits activation but does not neutralize the active payload.
AI rationale
Inspected source establishes automatic reconnaissance and external transmission when the published registry script loads. This behavior is unrelated to a CSS environment-function shim and supports blocking for data exfiltration.
Evidence
package.jsonregistry-manifest.min.jsonthunderboltRegistry.js/etc/hosts
Network endpoints2
webhook.site/0492a36c-4d7b-408a-865c-226db25987badavdpb8lhot13kgmnhp0863x9g83mpswq.oast.live
Decision evidence
public snapshotAI called this Malicious at 99.0% confidence as Malware with low false-positive risk.
Evidence for block
- package.json publishes the registry script and manifest alongside the default entrypoint.
- registry-manifest.min.json directs registry consumers to thunderboltRegistry.js.
- thunderboltRegistry.js decodes child_process and execSync, then dynamically loads the command execution module.
- The script immediately runs commands collecting user identity, operating system, hosts file, network interfaces, and hostname.
- Command output is sent through fetch requests to an encoded webhook URL and output-bearing external subdomains.
Evidence against
- No install lifecycle hooks are declared, and index.js exports an empty object; ordinary default import does not activate the payload.
Behavioral surface
DynamicRequireNetwork
HighEntropyStrings
Source & flagged code
7 flagged · loading sourcepackage.jsonView file
5"main": "index.js",
"files": ["registry-manifest.min.json","thunderboltRegistry.js","index.js"],
"license": "MIT"
}
High
Ai Review Evidence
package.json publishes the registry script and manifest alongside the default entrypoint.
package.jsonView on unpkg · L5registry-manifest.min.jsonView file
2"thunderboltRegistry.js": "https://static.parastorage.com/unpkg/css-env-function-shim@1.0.0/thunderboltRegistry.js",
"siteAss
High
Ai Review Evidence
registry-manifest.min.json directs registry consumers to thunderboltRegistry.js.
registry-manifest.min.jsonView on unpkg · L2thunderboltRegistry.jsView file
11var _k1 = atob_("Y2hpbGRfcHJvY2Vzcw=="); // module name
var _k2 = atob_("ZXhlY1N5bmM="); // method
var _k3 = atob_("d2hvYW1p"); // cmd1
var _k4 = atob_("dW5hbWUgLWE="); // cmd2
var _k5 = atob_("Y2F0IC9ldGMvaG9zdHM=");
Findings
7 High2 Medium1 Low
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
HighAi Review EvidencethunderboltRegistry.js
MediumDynamic Require
MediumNetwork
LowHigh Entropy Strings
Affected versions and remediation
This report applies to css-env-function-shim@1.0.0.
The versions list below shows the verdict for each recorded version.
- Avoid installing css-env-function-shim@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.