MAL-2026-4531

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Import Source

https://github.com/ossf/malicious-packages/blob/main/osv/malicious/npm/clsx-js/MAL-2026-4531.json

JSON Data

https://api.osv.dev/v1/vulns/MAL-2026-4531

Aliases

GHSA-8jmh-pvvx-wjrf

Published

2026-05-19T19:05:59Z

Modified

2026-06-09T15:31:28.932296043Z

Summary

Malicious code in clsx-js (npm)

Details

-= Per source details. Do not edit below this line.=-

Source: amazon-inspector (23e4e85f63d161234d84c774fdff696827934a27282be2ce9ff362a756246ee6)

On npm install, dist/postinstall.js base64-decodes the URL https://api.npoint.io/984b75c022a70cf00c39, fetches JSON from this anonymous mutable JSON-hosting service via axios, and pipes the response's data.content into a detached node child process's stdin for execution. The fetch has no version pin, no hash/signature verification, and the source is operator-mutable — the attacker can swap the executed payload at any time. The package additionally typosquats the widely-used clsx utility (by Luke Edwards): name is a one-token edit, and the description, author name, email, and homepage are copied verbatim from the legitimate clsx to impersonate the upstream maintainer. The genuine clsx ships no postinstall; this fork adds one whose only purpose is the remote-code dropper. A malformed Dependencies (capital-D) field also lists child_process, a known squat name. Installing this package on any machine results in arbitrary attacker-controlled code execution under the installer's user account.

Source: ghsa-malware (64650ce568f6dcb32276c86bc8e12ed0ea072a19425670e47310e7f4b3b01715)

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.

Database specific

{
    "malicious-packages-origins": [
        {
            "import_time": "2026-05-26T05:51:07.855735683Z",
            "versions": [
                "1.0.4"
            ],
            "sha256": "23e4e85f63d161234d84c774fdff696827934a27282be2ce9ff362a756246ee6",
            "id": "IN-MAL-2026-003696",
            "source": "amazon-inspector",
            "modified_time": "2026-05-21T01:34:43Z"
        },
        {
            "modified_time": "2026-05-19T19:05:59Z",
            "versions": [
                "1.0.3"
            ],
            "sha256": "2bc88378968921e5e583cd044040b7ac4c6a516c16741aa082d8e080c18329c0",
            "id": "IN-MAL-2026-003252",
            "source": "amazon-inspector",
            "import_time": "2026-05-26T05:50:17.815063977Z"
        },
        {
            "import_time": "2026-05-26T05:51:07.639262727Z",
            "versions": [
                "1.0.5"
            ],
            "sha256": "e280d8130a74a6db6f6960780c8e181e1abfcc2c759d9c31a3d987fa282d27bf",
            "id": "IN-MAL-2026-003694",
            "source": "amazon-inspector",
            "modified_time": "2026-05-21T01:33:56Z"
        },
        {
            "modified_time": "2026-06-09T14:47:43Z",
            "ranges": [
                {
                    "events": [
                        {
                            "introduced": "0"
                        }
                    ],
                    "type": "SEMVER"
                }
            ],
            "sha256": "64650ce568f6dcb32276c86bc8e12ed0ea072a19425670e47310e7f4b3b01715",
            "id": "GHSA-8jmh-pvvx-wjrf",
            "source": "ghsa-malware",
            "import_time": "2026-06-09T15:22:39.843009832Z"
        }
    ]
}

References

Credits

- Amazon Inspector - FINDER
- - actran@amazon.com

Affected packages

npm / clsx-js

Package

Name: clsx-js; View open source insights on deps.dev
Purl: pkg:npm/clsx-js

Affected ranges

Type: SEMVER
Events: Introduced

0Unknown introduced version / All previous versions are affected

Affected versions

1.*

1.0.3

1.0.4

1.0.5

Database specific

indicators

{
    "evidence_files": [
        {
            "sha256": "5f56892ba3e5445aeef5969d124d114477512fefd77a309082e3d77381c03d00",
            "tlsh": "17e0e52f723a67792f7009c4993296374d12d021f2c2e1e0a95d44576e87746450bfd8",
            "path": "dist/postinstall.js"
        },
        {
            "sha256": "f26866b6014efa39781457ef33410973c3129aae5f3356dd8cd7a4bd4c9b75f8",
            "tlsh": "8b21f328d4a44d6322da66e9a82e4157e960090b4b587e2833de416c8f4d69f90ff3de",
            "path": "package.json"
        }
    ],
    "package_integrity": [
        {
            "hashes": {
                "sha512_sri": "sha512-Uff8NiMf4/IPKA5kXpZxR6TUoa56QOrfT65DUzL/taNBgsrwD97tN1/YZV7tPr9sHlz1AiBhtPN+p3RiT3bTxQ==",
                "sha1": "75b0b4f73ec69708208258980071807772ecfd84"
            },
            "filename": "clsx-js-1.0.4.tgz"
        }
    ]
}

cwes

[
    {
        "description": "The product contains code that appears to be malicious in nature.",
        "name": "Embedded Malicious Code",
        "cweId": "CWE-506"
    },
    {
        "description": "The product contains code that appears to be malicious in nature.",
        "name": "Embedded Malicious Code",
        "cweId": "CWE-506"
    },
    {
        "description": "The product contains code that appears to be malicious in nature.",
        "name": "Embedded Malicious Code",
        "cweId": "CWE-506"
    },
    {
        "description": "The product contains code that appears to be malicious in nature.",
        "name": "Embedded Malicious Code",
        "cweId": "CWE-506"
    }
]

source

"https://github.com/ossf/malicious-packages/blob/main/osv/malicious/npm/clsx-js/MAL-2026-4531.json"