Stored XSS via unsanitized LESS output
Published Aug 26, 2026 · Updated Aug 27, 2026
Stored XSS in Winter CMS before 1.2.13 allows remote authenticated users to execute script in backend users' browsers. BrandSetting::renderCss returns LESS-compiled custom_css without removing HTML tags, so a crafted LESS escape can close the style element and inject script. Exploitation requires backend.manage_branding permission, and the script runs whenever another backend user loads a backend page.
Summary
What happened
Stored XSS in Winter CMS before 1.2.13 allows remote authenticated users to execute script in backend users' browsers. BrandSetting::renderCss returns LESS-compiled custom_css without removing HTML tags, so a crafted LESS escape can close the style element and inject script. Exploitation requires backend.manage_branding permission, and the script runs whenever another backend user loads a backend page.
The record
- CVE
- CVE-2026-32257
- Published
- Aug 26, 2026
- Updated
- Aug 27, 2026
- Vendor
- Winter CMS
- Product
- Winter CMS
- Classifications
- CWE-79, T1189
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 26, 2026CVE publishedPublication date reported by the CVE source.
- Aug 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.
- Affected versionversion=< 1.2.13
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- SecureLayer7 stored-XSS proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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