CVE-2026-8899Network attack vector

Contributor-level stored XSS via unescaped shortcode attributes

Published May 27, 2026 · Updated May 27, 2026

Stored XSS in Auto Thumbnails 1.0 and earlier allows remote authenticated users to inject scripts through the thumbnails shortcode. The athn_thumbnails() function concatenates the width and height attributes into an HTML image tag without sanitizing input or escaping output. Contributor-level access is required to save the shortcode in a page, and the injected script executes in the browser of each user who views that page.

CVSS severity6.4
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Auto Thumbnails 1.0 and earlier allows remote authenticated users to inject scripts through the thumbnails shortcode. The athn_thumbnails() function concatenates the width and height attributes into an HTML image tag without sanitizing input or escaping output. Contributor-level access is required to save the shortcode in a page, and the injected script executes in the browser of each user who views that page.

The record

CVE
CVE-2026-8899
Published
May 27, 2026
Updated
May 27, 2026
Vendor
gapgag55
Product
Auto Thumbnails
Classifications
CWE-79
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 27, 2026CVE publishedPublication date reported by the CVE source.
  2. May 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

gapgag55 · Auto Thumbnailsversion=0 <=1.0

Published CVSS scores

6.4WordfenceCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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