Zero-day vulnerability in Smart Slider 3

Embedded malicious code (backdoor)
CVE-2026-34424

Vulnerability details

Advisory: SB20260409111 - Backdoor in Nextend Smart Slider 3 Pro plugin for WordPress

Vulnerable component: Smart Slider 3

CVE-ID: CVE-2026-34424

CVSSv3 score: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:H/RL:O/RC:C

CWE-ID: CWE-506 - Embedded Malicious Code

Description:

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.

External links:

https://patchstack.com/articles/critical-supply-chain-compromise-in-smart-slider-3-pro-full-malware-...

About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.