Detect CVE-2026-47428: Vitest Browser Mode XSS via Unsanitized otelCarrier Query Parameter in Elastic Security
CVE-2026-47428 is a reflected Cross-Site Scripting (XSS) vulnerability in @vitest/browser versions >= 4.0.17 < 4.1.6 and >= 5.0.0-beta.0 < 5.0.0-beta.3. The browser mode development server serves the otelCarrier query parameter as unsanitized inline script content in esm-client-injector.js and serverOrchestrator.ts, allowing an attacker to inject arbitrary JavaScript into the test runner's browser context. With a CVSS of 9.6 and public PoC available, this poses a critical risk to CI/CD pipelines and developer workstations running Vitest browser mode tests, potentially enabling credential theft, session hijacking, or supply chain compromise.
MITRE ATT&CK
Elastic Detection Query
sequence by host.name with maxspan=5m
[network where network.protocol == "http" and
url.query : "*otelCarrier*" and
url.query : ("*<*", "*>*", "*script*", "*javascript*", "*onerror*", "*onload*")]
[process where process.name in ("node", "node.exe") and
process.args : ("*vitest*", "*@vitest/browser*")]EQL sequence detection correlating suspicious otelCarrier HTTP requests containing XSS payloads with subsequent Node.js Vitest browser mode process execution, indicating active CVE-2026-47428 exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate OpenTelemetry instrumentation where otelCarrier values contain encoded characters that match XSS patterns
- Authorized penetration testing or red team exercises targeting Vitest-based developer environments
- Automated DAST tools scanning developer workstations as part of a security assessment
- URL parsers or logging systems that decode and re-encode query parameters in ways that trigger pattern matches
Other platforms for CVE-2026-47428
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1CVE-2026-47428 Basic XSS via otelCarrier Parameter
Expected signal: HTTP request logs showing otelCarrier parameter containing <script> tags; Node.js process spawning on port 5173; outbound network connection to attacker.lab if XSS executes successfully in browser
- Test 2CVE-2026-47428 Event Handler XSS Payload Variant
Expected signal: HTTP requests with onerror, onload event handler patterns in otelCarrier; DNS/network connections to attacker.lab from browser process if XSS executes; browser process network activity on non-standard ports
- Test 3CVE-2026-47428 CI/CD Pipeline Exploitation Simulation
Expected signal: Node.js process with vitest and --browser arguments; child browser process (Chromium/Playwright) spawned from test runner; outbound HTTP connections from browser process to external host; environment variable access logged by audit framework
References (4)
- https://github.com/vitest-dev/vitest/security/advisories/GHSA-2h32-95rg-cppp
- https://github.com/vitest-dev/vitest/blob/cba2036a197ec8ed42c35a37db78ef07192202c7/packages/browser/src/client/public/esm-client-injector.js#L41
- https://github.com/vitest-dev/vitest/blob/cba2036a197ec8ed42c35a37db78ef07192202c7/packages/browser/src/node/serverOrchestrator.ts#L48
- https://github.com/advisories/GHSA-2h32-95rg-cppp
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