SB20260409111 - Backdoor in Nextend Smart Slider 3 Pro plugin for WordPress
Published: April 9, 2026 Updated: September 20, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 1 vulnerability.
1) Embedded malicious code (backdoor) (CVE-ID: CVE-2026-34424) Exploited
CWE-ID: CWE-506 - Embedded Malicious Code
CVSSv4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to gain unauthorized access to the application.
The vulnerability exists due to presence of embedded malicious functionality in the application code (aka backdoor) that allows a remote attacker to gain unauthorized access to the application.
Note, an unauthorized party gained access to Nextend update infrastructure on April 7 and distributed a fully attacker-authored build through the official update channel. Only version 3.5.1.35 contained the backdoor code.
Remediation
Install update from vendor's website.
References
- https://mysites.guru/blog/smart-slider-3-pro-supply-chain-compromise/
- https://patchstack.com/articles/critical-supply-chain-compromise-in-smart-slider-3-pro-full-malware-analysis/
- https://patchstack.com/database/wordpress/plugin/nextend-smart-slider3-pro/vulnerability/wordpress-smart-slider-3-plugin-3-5-1-35-backdoor-vulnerability
- https://smartslider.helpscoutdocs.com/article/2143-joomla-security-advisory-smart-slider-3-pro-3-5-1-35-compromise
- https://smartslider.helpscoutdocs.com/article/2144-wordpress-security-advisory-smart-slider-3-pro-3-5-1-35-compromise