Open-Source Security Intelligence

Know every vulnerability
before it knows you.

DevGuard continuously monitors your dependencies and alerts you when CVEs like this one affect your stack — with real-time threat intelligence built for developers.

Checkout DevGuardView on GitHub
Search

GHSA-5h9g-x5rv-25wg

MediumCVSS 6.1 / 10
Published Oct 22, 2021·Last modified Feb 4, 2026
Affected Components(0)

No affected components available

Description

Impact

A cross-site scripting (XSS) vulnerability was discovered in the schema validation logic of the core parser. The vulnerability allowed arbitrary JavaScript execution when inserting a specially crafted piece of content into the editor using the clipboard or editor APIs. This malicious content could then end up in content published outside the editor, if no server-side sanitization was performed. This impacts all users who are using TinyMCE 5.8.2 or lower.

Patches

This vulnerability has been patched in TinyMCE 5.9.0 by ensuring schema validation was still performed after unwrapping invalid elements.

Workarounds

To work around this vulnerability, either:

  • Upgrade to TinyMCE 5.9.0 or higher
  • Manually sanitize the content using the BeforeSetContent event (see below)

Example: Manually sanitize content

editor.on('BeforeSetContent', function(e) {
  var sanitizedContent = ...; // Manually sanitize content here
  e.content = sanitizedContent;
});

Acknowledgements

Tiny Technologies would like to thank William Bowling for discovering this vulnerability.

References

https://www.tiny.cloud/docs/release-notes/release-notes59/#securityfixes

For more information

If you have any questions or comments about this advisory:

Risk Scores
Base Score
6.1

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence
5.6

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
1.07%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

Browse More

Medium severity
Scan your project

Continuously monitor your dependencies and get alerted when vulnerabilities like this one affect your stack.

Checkout DevGuard