Summary
Failing to properly encode user input, online media asset rendering (*.youtube and *.vimeo files) is vulnerable to cross-site scripting. A valid backend user account or write access on the server system (e.g. SFTP) is needed in order to exploit this vulnerability.
Impact
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
GHSA-WG8H-GXF4-G4GH has a CVSS score of 6.1 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (8.7.21, 9.5.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
typo3/cms-core to 8.7.21 or later; typo3/cms-core to 9.5.2 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is GHSA-WG8H-GXF4-G4GH? GHSA-WG8H-GXF4-G4GH is a medium-severity cross-site scripting (XSS) vulnerability in typo3/cms-core (composer), affecting versions >= 8.0.0, < 8.7.21. It is fixed in 8.7.21, 9.5.2. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- How severe is GHSA-WG8H-GXF4-G4GH? GHSA-WG8H-GXF4-G4GH has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of typo3/cms-core are affected by GHSA-WG8H-GXF4-G4GH? typo3/cms-core (composer) versions >= 8.0.0, < 8.7.21 is affected.
- Is there a fix for GHSA-WG8H-GXF4-G4GH? Yes. GHSA-WG8H-GXF4-G4GH is fixed in 8.7.21, 9.5.2. Upgrade to this version or later.
- Is GHSA-WG8H-GXF4-G4GH exploitable, and should I be worried? Whether GHSA-WG8H-GXF4-G4GH is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-WG8H-GXF4-G4GH is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-WG8H-GXF4-G4GH?
- Upgrade
typo3/cms-coreto 8.7.21 or later - Upgrade
typo3/cms-coreto 9.5.2 or later
- Upgrade