TI-2021-16690 Aliases CVE-2021-39318 GHSA-777j-8c2c-w27p

H5P CSS Editor <= 1.0 Reflected Cross-Site Scripting

LOW 29CWE-79Published 2021-12-14 · Updated 2025-02-13

Key facts

Attack vector: Network
Privileges required: None
User interaction: Required
Attack complexity: Low
Impact type: Cross-site scripting
Confidentiality · integrity · availability: Low · Low · None
Fix status: No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-79.

Summary

The H5P CSS Editor WordPress plugin is vulnerable to Reflected Cross-Site Scripting via the h5p-css-file parameter found in the ~/h5p-css-editor.php file which allows attackers to inject arbitrary web scripts, in versions up to and including 1.0.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00782 56th percentileScored 2026-11-07

Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
H5P CSS Editor	H5P CSS Editor	1.0 – 1.0	—	No fix listed	CNA

H5P CSS Editor VendorH5P CSS Editor Affected 1.0 – 1.0 Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:h5p-css-editor_project:h5p-css-editor::::::wordpress::*	up to 1.0	Vulnerable	H5p-css-editor Project

cpe:2.3:a:h5p-css-editor_project:h5p-css-editor:*:*:*:*:*:wordpress:*:* Versions up to 1.0 Vulnerable ·H5p-css-editor Project

Remediation

No fixed version listed by the sources yet.

Timeline

2026-10-02 Threatist record created from CVE-2021-39318
2026-10-03 Alias added: GHSA-777j-8c2c-w27p

References

Advisory 2

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences