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CVE-2026-8899

MEDIUMCVSS 6.4/10EPSS 0.20%

Last modified

CVE-2026-8899 is a medium-severity vulnerability rated 6.4/10 on the CVSS scale. The Auto Thumbnail plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'thumbnails' shortcode in all versions up to, and including, 1.0. This is due to insufficient input sanitization and output escaping on the shortcode's 'width' and 'height' attributes in the athn_thumbnails() function, which are concatenated directly into an HTML <img> tag. EPSS estimates a 0.20% chance of exploitation in the next 30 days.

Description

The Auto Thumbnail plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'thumbnails' shortcode in all versions up to, and including, 1.0. This is due to insufficient input sanitization and output escaping on the shortcode's 'width' and 'height' attributes in the athn_thumbnails() function, which are concatenated directly into an HTML <img> tag. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

Metrics

CVSS 3.1
6.4/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

EPSS Probability
0.20%

9.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

References

Timeline

Published
Last Modified
Status
Deferred

Frequently Asked Questions

What is CVE-2026-8899?
The Auto Thumbnail plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'thumbnails' shortcode in all versions up to, and including, 1.0. This is due to insufficient input sanitization and output escaping on the shortcode's 'width' and 'height' attributes in the athn_thumbnails() function, which are concatenated directly into an HTML <img> tag. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
How severe is CVE-2026-8899?
CVE-2026-8899 has a CVSS score of 6.4/10 (MEDIUM severity). The EPSS model estimates a 0.20% probability of exploitation in the next 30 days.
How do I fix CVE-2026-8899?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST