CVE-2026-15421

Speed Optimizer <= 7.8.0 - Authenticated (Contributor+) Stored Cross-Site Scripting via Image Tag Attributes

The Speed Optimizer – The All-In-One Performance-Boosting Plugin plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Image Tag Attributes in all versions up to, and including, 7.8.0 due to insufficient input sanitization and output escaping. 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. This is only exploitable when the site administrator has enabled the Lazy Load Media option in the plugin settings.

We have discovered 10,782 live websites that are affected by CVE-2026-15421.

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Affected Software

Product  SG Optimizer
Category Cache Tools
Vulnerable Domains10,782 live websites (100% of SG Optimizer install base)
Vulnerable Versions
  • from 0 through 7.8
Vulnerable Versions Count70 versions ( 100% of all versions)


Common Weakness Enumeration

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



Details

  • Published - Aug 19, 2026
  • Updated - Aug 20, 2026

Credits

  • stealthcopter (finder)

Website Distribution by Country

Number of websites using CVE-2026-15421
United States6,209 websites


GB957 websites
Italy655 websites
Australia363 websites
Canada356 websites
Germany319 websites
Spain245 websites
Netherlands241 websites
Cyprus148 websites
France122 websites

Website Distribution by TLD

Number of websites using CVE-2026-15421
.com5,726 websites
.co.uk778 websites
.org691 websites
.it651 websites
.com.au376 websites
.nl274 websites
.ca229 websites
.net225 websites
.de156 websites
.es138 websites

Vulnerable Versions

Vulnerable versions are highlighted in red

Websites affected by CVE-2026-15421

Top websites that are affected by CVE-2026-15421. Please click on the "Contact us" link to get more information.
DomainCountryRankContacts
************.**.uk GB**,***
*************.com United States**,***
*******************.net United States**,***
***************.**.uk United States**,***
**********.org United States**,***
**********.net United States**,***
********************.com United States**,***
***************.com Belgium**,***
********.net United States**,***
*******.org United States**,***
See full domain list

FAQ

CVE-2026-15421 is Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in SG Optimizer
A total of 10,782 websites have been identified as vulnerable to CVE-2026-15421, based on global website indexing conducted by WebTechSurvey.
The SG Optimizer is affected by the CVE-2026-15421 vulnerability.
SG Optimizer versions up to and including 7.8 are vulnerable to CVE-2026-15421.

References