GHSA-866w-xmhq-wj7x is a medium-severity (CVSS 4.3) CWE-1321 vulnerability in @sveltejs/kit. O3 Security confirms whether GHSA-866w-xmhq-wj7x is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
SvelteKit: Prototype pollution in file input deletion path in remote-function forms
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-866w-xmhq-wj7x.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-866w-xmhq-wj7x plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 369,023 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@sveltejs/kitnpmDescription
If you use remote form functions, have an input field of type file, and accept arbitrary user-controlled path names for the field, then you are vulnerable to a prototype pollution attack where the attacker can remove e.g. methods on the prototype.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @sveltejs/kit | all versions | 2.69.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @sveltejs/kit. 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 @sveltejs/kit to 2.69.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-866w-xmhq-wj7x 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-866w-xmhq-wj7x 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-866w-xmhq-wj7x. 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-866w-xmhq-wj7x in your dependencies?
O3 detects GHSA-866w-xmhq-wj7x across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.