Cross-site scripting vulnerability in TinyMCE
Impact
A cross-site scripting (XSS) vulnerability was discovered in the URL sanitization logic of the core parser for form elements. The vulnerability allowed arbitrary JavaScript execution when inserting a specially crafted piece of content into the editor using the clipboard or APIs, and then submitting the form. However, as TinyMCE does not allow forms to be submitted while editing, the vulnerability could only be triggered when the content was previewed or rendered outside of the editor. This impacts all users who are using TinyMCE 5.7.0 or lower.
Patches
This vulnerability has been patched in TinyMCE 5.7.1 by improved URL sanitization logic.
Workarounds
To work around this vulnerability, either:
- Upgrade to TinyMCE 5.7.1 or higher
- Manually sanitize
formURL attributes using a TinyMCE node filter. - Disable
formelements in your content using the invalid_elements setting.
Example: Sanitizing using a node filter
editor.parser.addNodeFilter('form', function(nodes) {
nodes.forEach(function(node) {
if (node.attributes) {
node.attributes.forEach(function(attr) {
var name = attr.name;
var value = attr.value;
// Sanitize the attribute value here or remove it entirely
var sanitizedValue = ...;
node.attr(name, santizedValue);
});
}
});
});Example: Using invalid_elements
invalid_elements: 'form'Acknowledgements
Tiny Technologies would like to thank Mikhail Khramenkov at Solar Security Research Team for discovering this vulnerability.
References
https://www.tiny.cloud/docs/release-notes/release-notes571/#securityfixes
For more information
If you have any questions or comments about this advisory:
- Open an issue in the TinyMCE repo
- Email us at infosec@tiny.cloud
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | tinymce | < 5.7.1 | 5.7.1 |
References
- Weakness (CWE)
CWE-79- Platform
- npm
- Package
tinymce- Disclosed
- 28.05.2021
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-5vm8-hhgr-jcjp - CC BY 4.0
Vulnerability history: tinymce
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 20
- First → latest
- 01.2020 06.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 5
- Medium 14
- Low 1
Disclosures per year
- 2020: 3
- 2021: 5
- 2022: 1
- 2023: 3
- 2024: 4
- 2025: 0
- 2026: 4
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