Stored XSS via lazy-load image attributes
Published Aug 19, 2026 · Updated Aug 20, 2026
Stored XSS in Lazy Load Media in SiteGround Speed Optimizer before 7.8.1 allows remote authenticated users to execute script via image attributes. The public record places the flaw in the plugin's Lazy_Load image-processing path, which rewrites img tag attributes for lazy loading and insufficiently sanitizes and escapes that attribute content. Exploitation requires contributor-level access or higher and the administrator to have enabled Lazy Load Media; payloads then run in the browsers of users who open the poisoned page.
Summary
What happened
Stored XSS in Lazy Load Media in SiteGround Speed Optimizer before 7.8.1 allows remote authenticated users to execute script via image attributes. The public record places the flaw in the plugin's Lazy_Load image-processing path, which rewrites img tag attributes for lazy loading and insufficiently sanitizes and escapes that attribute content. Exploitation requires contributor-level access or higher and the administrator to have enabled Lazy Load Media; payloads then run in the browsers of users who open the poisoned page.
The record
- CVE
- CVE-2026-15421
- Published
- Aug 19, 2026
- Updated
- Aug 20, 2026
- Vendor
- SiteGround
- Product
- Speed Optimizer
- Classifications
- CWE-79, T1059.007
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 19, 2026CVE publishedPublication date reported by the CVE source.
- Aug 20, 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=0 <=7.8.0
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
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Technologies
Your stack
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Your stack
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