PatchSiren cyber security CVE debrief

CVE-2025-15678 Nexter Blocks CVE debrief

The Nexter Blocks WordPress plugin before 5.0.2 does not sanitize uploaded SVG files and allows SVG uploads for any user able to upload files (Author by default), allowing them to upload a file containing malicious JavaScript that executes when the file is accessed, leading to Stored Cross-Site Scripting. This vulnerability has significant implications for users with author-level access or higher, as it can lead to unauthorized code execution and potential data breaches. It is crucial for administrators to verify the plugin version, restrict file uploads to trusted users, and implement additional security measures to detect and prevent malicious file uploads. Furthermore, reviewing compensating controls for exposed systems and monitoring for suspicious activity are essential steps in mitigating this vulnerability.

Vendor: Nexter Blocks
Product: Nexter Blocks WordPress plugin
CVSS: MEDIUM 6.1
CISA KEV: Not listed in stored evidence
Original CVE published: 2026-08-06
Original CVE updated: 2026-08-06
Advisory published: 2026-08-06
Advisory updated: 2026-08-06

Who should care

Users of the Nexter Blocks WordPress plugin, especially those with author-level access or higher, should be aware of this vulnerability and take steps to mitigate it. This includes verifying the plugin version, restricting file uploads, and implementing additional security measures to detect and prevent malicious file uploads. Security teams and vulnerability management teams should also review the affected scope and severity to ensure proper prioritization and remediation.

Technical summary

The Nexter Blocks WordPress plugin before version 5.0.2 does not sanitize uploaded SVG files, allowing users with file upload capabilities to upload malicious JavaScript-containing files. These files execute when accessed, leading to Stored Cross-Site Scripting. This vulnerability has a CVSS score of 6.1 and is classified as MEDIUM severity. The vulnerability affects users with author-level access or higher.

Defensive priority

Medium priority due to the CVSS score of 6.1 and the potential for Stored Cross-Site Scripting.

Recommended defensive actions

Inventory and verify the Nexter Blocks WordPress plugin version.
Restrict file uploads to only trusted users.
Implement additional security measures to detect and prevent malicious file uploads.
Monitor for suspicious activity and update the plugin to version 5.0.2 or later.
Review compensating controls for exposed systems while remediation is scheduled and verified.
Check relevant monitoring, detection, and logs for exposed assets that need extra review.
Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The evidence for this CVE is limited, primarily based on official records from CVE.org and NVD. The Nexter Blocks WordPress plugin before version 5.0.2 does not sanitize uploaded SVG files, allowing users with file upload capabilities to upload malicious JavaScript-containing files. These files execute when accessed, leading to Stored Cross-Site Scripting. Further verification is recommended to confirm affected scope and severity. Defenders should verify the plugin version, review user access controls, and monitor for suspicious activity.

Official resources

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-08-06T07:16:26.660Z and has not been modified since then.