GHSA-vj5c-m527-mpff is a high-severity (CVSS 8.8) CWE-1321 vulnerability in style-dictionary. O3 Security confirms whether GHSA-vj5c-m527-mpff is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Style Dictionary - Prototype Pollution in convertTokenData utility function
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
style-dictionarynpmDescription
Impact
Prototype pollution.
A malicious user can create a token array [{ key: '{__proto__.foo}', value: 'malicious' }], when processed by convertTokenData() utility function, it will pollute the Object.prototype globally where {}.foo will equal { key: '{__proto__.foo}', value: 'malicious' }.
This has been confirmed with a test/reproduction.
You are impacted when:
- direct usage of
convertTokenData(tokens, { output: 'object' }); - indirect usage, via using Expand API https://styledictionary.com/reference/config/#expand. If your expand config deems it necessary to run expand (this means, if NOT: 1) set to false, 2) all subprops set to false, or 3) undefined), then we sync the
sd.tokensproperty with thesd.tokenMapproperty by converting tokenData map back to object. - indirect usage via SD's transform lifecycle. Once your tokens are transformed, we also have to sync the
sd.tokensproperty with thesd.tokenMapproperty.
Impact is high for this when style-dictionary is used as an integration in a NodeJS server application. Impact is moderate for when style-dictionary is used as an integration in a Web application. Impact is low for most common cases where the user of style-dictionary also maintains the tokens, and access is limited via read/write access to the repository/workflows where it is used.
Patches
A patch has been published: version 5.4.4.
Any version within range >=4.3.0 <5.4.4 contains this vulnerability, see commit hash 209085d for when the vulnerability was added.
See PR with repro + fix https://github.com/style-dictionary/style-dictionary/pull/1702
Workarounds
A workaround is to sanitize your token data first. Whether using DTCG format or old Style Dictionary format, you have to check the token data object recursively for any object keys that include __proto__.
You can do this with the StyleDictionary instance too, just ensure that expand has to be set to false to prevent the second method of this vulnerability from happening.
const sd = new StyleDictionary({ expand: false });
if (sd.allTokens.some(tok => tok.key.includes('__proto__')) {
throw new Error('Found malicious token key, attempting to do prototype pollution.')
}
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | style-dictionary | ≥ 4.3.0&&< 5.4.4 | 5.4.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for style-dictionary. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update style-dictionary to 5.4.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vj5c-m527-mpff is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-vj5c-m527-mpff is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-vj5c-m527-mpff. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-vj5c-m527-mpff in your dependencies?
O3 detects GHSA-vj5c-m527-mpff across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.