CVE-2026-4022 in Show Posts list Plugin
Summary
by MITRE • 03/21/2026
The Show Posts list – Easy designs, filters and more plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'post_type' shortcode attribute in the 'swiftpost-list' shortcode in all versions up to, and including, 1.1.0 due to insufficient input sanitization and output escaping on user-supplied attributes. 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.
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Analysis
by VulDB Data Team • 03/21/2026
The vulnerability identified as CVE-2026-4022 affects the Show Posts list plugin for WordPress, specifically targeting versions through 1.1.0. This plugin provides functionality for displaying posts with various design options, filters, and customization features. The security flaw resides within the swiftpost-list shortcode implementation where the 'post_type' attribute fails to properly sanitize user input before processing. The vulnerability represents a classic stored cross-site scripting vulnerability that allows authenticated attackers with contributor-level privileges or higher to inject malicious scripts into the plugin's shortcode processing mechanism. This type of vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws in software applications.
The technical exploitation of this vulnerability occurs through the manipulation of the 'post_type' shortcode attribute within the swiftpost-list shortcode. When an authenticated user with contributor access creates or modifies a post containing a maliciously crafted shortcode, the vulnerable plugin fails to properly escape or sanitize the input data before storing it in the database. This stored malicious content then gets executed whenever any user accesses pages containing the affected shortcode, making it a persistent threat. The vulnerability impacts all users who view pages with the compromised shortcode, regardless of their privilege level, as the malicious script executes in the context of their browser session.
The operational impact of this vulnerability extends beyond simple script execution as it creates a persistent backdoor for attackers to maintain access to compromised WordPress installations. Contributors and above can leverage this vulnerability to inject malicious JavaScript that could steal session cookies, redirect users to phishing sites, or even establish command and control channels. The attack vector is particularly concerning because it requires only contributor-level privileges, which are commonly granted to trusted users, content editors, or even automated systems. This makes the vulnerability particularly dangerous in multi-user environments where such accounts are frequently used. The stored nature of the XSS means that even if the initial injection is discovered and removed, the malicious payload remains active and continues to affect users who access the compromised pages.
Mitigation strategies for this vulnerability should include immediate patching of the Show Posts list plugin to version 1.1.1 or later, which contains the necessary sanitization fixes. Organizations should also implement strict input validation for all shortcode attributes and ensure proper output escaping before rendering user-supplied content. Security monitoring should include scanning for malicious shortcodes in posts and pages, particularly those created by users with contributor privileges or higher. The vulnerability aligns with ATT&CK technique T1566.001 which covers phishing with malicious attachments, as attackers can use the stored XSS to redirect users to malicious sites. Additionally, implementing a content security policy can provide an additional layer of protection against script execution, though this should not replace proper input sanitization. Regular security audits of WordPress plugins and themes should be conducted to identify similar vulnerabilities, as this represents a common pattern in WordPress plugin development where insufficient sanitization leads to XSS vulnerabilities.