CVE-2026-1827: Flask Micro Code-Editor XSS Vulnerability

CVE-2026-1827 Overview

The Flask Micro code-editor plugin for WordPress contains a Stored Cross-Site Scripting (XSS) vulnerability in the plugin's codeflask shortcode. All versions up to and including 1.0.0 are affected due to insufficient input sanitization and output escaping on user-supplied attributes. This vulnerability enables authenticated attackers with contributor-level access or above to inject arbitrary web scripts into WordPress pages, which execute whenever a user accesses the compromised page.

Critical Impact

Authenticated attackers can inject persistent malicious scripts that execute in visitors' browsers, potentially leading to credential theft, session hijacking, or malware distribution through compromised WordPress sites.

Affected Products

• Flask Micro code-editor plugin for WordPress versions ≤ 1.0.0
• WordPress installations with the Flask Micro plugin enabled
• Sites allowing contributor-level or higher user access

Discovery Timeline

• 2026-02-11 - CVE-2026-1827 published to NVD
• 2026-02-11 - Last updated in NVD database

Technical Details for CVE-2026-1827

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The Flask Micro plugin fails to properly sanitize and escape user-controlled input within its shortcode handler, specifically in the flask_micro.php file around line 80. When a contributor or higher-privileged user creates or edits content using the codeflask shortcode, they can embed malicious JavaScript payloads within shortcode attributes. These payloads are stored in the WordPress database and rendered without proper escaping when the page is viewed.

The vulnerability requires network access and a low-privileged authenticated account (contributor role), but requires no user interaction for the injected script to execute. The scope is changed, meaning the vulnerability can affect resources beyond the vulnerable component—specifically, it can impact website visitors who view the infected page.

Root Cause

The root cause lies in the plugin's shortcode processing function within flask_micro.php. The code fails to implement proper input validation and output encoding when handling user-supplied attributes in the codeflask shortcode. WordPress shortcodes allow authors to embed dynamic content, but when attribute values are not sanitized using functions like esc_attr(), esc_html(), or wp_kses(), attackers can inject HTML and JavaScript that breaks out of the intended context.

Attack Vector

The attack requires an authenticated user with at least contributor-level access to WordPress. The attacker crafts a malicious shortcode containing JavaScript payload within the attributes, then publishes or saves it as a draft (depending on their role permissions). When any user, including administrators, views the page containing this shortcode, the malicious script executes in their browser context. This can lead to session token theft, administrative account compromise, defacement, or redirection to malicious sites.

The attack flow involves:

1. Attacker obtains contributor or higher access to the WordPress site
2. Attacker creates a post or page using the vulnerable codeflask shortcode with malicious attributes
3. The content is stored in the WordPress database
4. When visitors or administrators view the page, the XSS payload executes in their browser

For detailed technical analysis, see the Wordfence Vulnerability Analysis and the plugin source code.

Detection Methods for CVE-2026-1827

Indicators of Compromise

• Unusual or obfuscated JavaScript code within WordPress post content using the codeflask shortcode
• Posts or pages containing codeflask shortcode attributes with encoded characters, script tags, or event handlers (e.g., onload, onerror, onclick)
• Unexpected outbound connections from visitor browsers to unknown domains when viewing specific pages
• Reports from users about browser warnings, unexpected redirects, or credential prompts when viewing WordPress content

Detection Strategies

• Review WordPress database content (specifically wp_posts table) for suspicious codeflask shortcode usage containing JavaScript or encoded payloads
• Implement Web Application Firewall (WAF) rules to detect and block XSS patterns in shortcode attributes
• Monitor contributor and author user activity logs for unusual content creation patterns
• Deploy Content Security Policy (CSP) headers to detect and report inline script execution attempts

Monitoring Recommendations

• Enable WordPress security audit logging to track post creation and modification by users with contributor access or higher
• Configure browser-based XSS detection through CSP reporting to identify exploitation attempts
• Regularly scan WordPress content for known XSS payload patterns using security plugins or automated tools

How to Mitigate CVE-2026-1827

Immediate Actions Required

• Audit all existing posts and pages using the codeflask shortcode for suspicious content
• Temporarily disable the Flask Micro plugin until a patched version is available
• Review and revoke contributor-level access for untrusted users
• Implement Content Security Policy headers to limit the impact of any injected scripts

Patch Information

As of the last NVD update on 2026-02-11, no official patch has been documented. Monitor the WordPress plugin repository and the Wordfence vulnerability advisory for updates on a fixed version. Site administrators should check the plugin's changelog and update immediately when a patched release becomes available.

Workarounds

• Deactivate the Flask Micro plugin from the WordPress admin panel until a security update is released
• Restrict contributor and author role assignments to trusted users only
• Implement a Web Application Firewall with XSS filtering rules to provide an additional layer of defense
• Add strict Content Security Policy headers to prevent execution of inline scripts

# Apache configuration to add Content Security Policy header
# Add to .htaccess or Apache configuration file
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none';"