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Security Advisory

WordPress 5.1.1: 42 Critical Security Vulnerabilities Explained

📅 May 31, 2026 ·⏱ 5 min read ·🔒 SiteRecipe Security Team
9,650 websites still running wordpress 5.1.1  → View full list
42
Total
3
Critical
9
High
30
Medium

WordPress 5.1.1 is a vulnerable version with 42 documented security vulnerabilities, including 3 critical-level flaws that can compromise your entire website. If you're running this outdated version, hackers can exploit authentication bypasses, unauthorized password resets, and privilege escalation attacks. This guide will help you identify if your site is at risk and provide immediate steps to secure your WordPress installation.

Approximately 9000+ websites still run WordPress 5.1.1, making them easy targets for automated attacks. The most dangerous vulnerabilities include authentication bypass in the UserPro plugin, unauthorized password resets, and privilege escalation in popular contact form plugins. We'll walk you through checking your version and implementing fixes to protect your business.

What is Wordpress 5.1.1?

WordPress 5.1.1 is an older version of WordPress, the platform that powers over 43% of all websites on the internet. Released in early 2019, this version is no longer supported by the WordPress development team, meaning security patches are no longer released. When WordPress versions stop receiving updates, they become increasingly vulnerable to hackers who exploit known weaknesses.

Think of WordPress like the foundation of your house—when it's outdated and unmaintained, cracks appear that burglars can use to break in. Version 5.1.1 has multiple "cracks" in its code, some of which allow attackers to take control of user accounts, reset passwords without permission, or gain administrator access without proper credentials. Running an outdated WordPress version is one of the biggest security risks any website owner can take.

Key Vulnerabilities in Wordpress 5.1.1

42 CVEs found. The most critical are explained below.

CRITICAL CVE-2023-2437 9.8/10 · CVSS v3.1 ⏱ Immediate
UserPro Plugin - Attackers Can Log In As Anyone

The UserPro plugin has a serious flaw in its Facebook login feature that doesn't properly verify who is trying to log in. This means someone could pretend to be any existing user on your website without needing their password.

Impact: Attackers could access any user account, steal customer data, modify content, or take over admin accounts to control your entire website.

↗ View on NVD
CRITICAL CVE-2023-2449 9.8/10 · CVSS v3.1 ⏱ Immediate
UserPro Plugin - Unauthorized Password Resets

The UserPro plugin's password reset feature doesn't properly check if the person requesting a reset should actually be allowed to reset that password. Attackers can exploit this to reset passwords for any account.

Impact: Hackers can reset passwords for any user account, including administrators, giving them complete access to those accounts without knowing the original passwords.

↗ View on NVD
CRITICAL CVE-2024-2771 9.8/10 · CVSS v3.1 ⏱ Immediate
Fluent Forms Plugin - Unprivileged Users Get Admin Powers

The Fluent Forms plugin is missing a security check that would normally prevent regular users from accessing admin functions. This allows low-level users to perform actions only administrators should be able to do.

Impact: Attackers with basic user accounts can escalate their permissions to administrator level, gaining full control over your website and all its data.

↗ View on NVD
HIGH CVE-2019-9787 8.8/10 · CVSS v3.0 ⏱ Immediate
WordPress Core - Comments Can Execute Malicious Code

WordPress versions before 5.1.1 don't properly filter what visitors type in comments, and a security protection called CSRF is not working correctly. This allows attackers to inject malicious code through comments.

Impact: Hackers can inject harmful code into your website through comments that executes on visitors' browsers, potentially stealing data or redirecting users to malicious sites.

↗ View on NVD
HIGH CVE-2023-2440 8.8/10 · CVSS v3.1 ⏱ Within 7 days
UserPro Plugin - Missing Security Tokens in Forms

The UserPro plugin doesn't use proper security tokens (called nonces) to verify that form submissions are legitimate and come from your own website. This makes it vulnerable to Cross-Site Request Forgery attacks.

Impact: Attackers can trick users into unknowingly making changes to their accounts or website settings through malicious links or websites, even without logging in.

↗ View on NVD
HIGH CVE-2025-3952 8.1/10 · CVSS v3.1 ⏱ Within 7 days
Projectopia Plugin - Users Can Crash Website Features

The Projectopia project management plugin is missing a security check on one of its functions, allowing users without proper permissions to remove important logo files and disable functionality.

Impact: Unauthorized users can remove logos or damage website functionality, potentially causing your site to display incorrectly or stop working properly.

↗ View on NVD

Additional Vulnerabilities (36 more)

Showing first 10 of 36. View all on NVD ↗

CVE IDSeverityScore PublishedDescription
CVE-2026-5436 HIGH 8.1 2026-04-08 The MW WP Form plugin for WordPress is vulnerable to Arbitrary File Move/Read in all versions up to and including 5.1.1. This is due to insufficient validation of the $name parame…
CVE-2024-31210 HIGH 7.6 2024-04-04 WordPress is an open publishing platform for the Web. It's possible for a file of a type other than a zip file to be submitted as a new plugin by an administrative user on the Plu…
CVE-2024-2782 HIGH 7.5 2024-05-18 The Contact Form Plugin by Fluent Forms for Quiz, Survey, and Drag & Drop WP Form Builder plugin for WordPress is vulnerable to unauthorized modification of data due to a missing …
CVE-2024-4157 HIGH 7.5 2024-05-22 The Contact Form Plugin by Fluent Forms for Quiz, Survey, and Drag & Drop WP Form Builder plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and inc…
CVE-2025-13457 HIGH 7.5 2026-01-10 The WooCommerce Square plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 5.1.1 via the get_token_by_id function due to …
CVE-2023-6007 HIGH 7.3 2023-11-22 The UserPro plugin for WordPress is vulnerable to unauthorized access of data, modification of data, loss of data due to a missing capability check on multiple functions in all ve…
CVE-2023-2446 MEDIUM 6.5 2023-11-22 The UserPro plugin for WordPress is vulnerable to sensitive information disclosure via the 'userpro' shortcode in versions up to, and including 5.1.1. This is due to insufficient …
CVE-2025-9260 MEDIUM 6.5 2025-09-03 The Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder plugin for WordPress is vulnerable to PHP Object Injection in versions 5.1.16 to 6.1.1 v…
CVE-2024-2772 MEDIUM 6.4 2024-05-18 The Contact Form Plugin by Fluent Forms for Quiz, Survey, and Drag & Drop WP Form Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via form settings in al…
CVE-2024-4709 MEDIUM 6.4 2024-05-18 The Contact Form Plugin by Fluent Forms for Quiz, Survey, and Drag & Drop WP Form Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘subject’ param…
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How to Check If Your Website Is Affected

How to Fix These Vulnerabilities

Conclusion

WordPress 5.1.1 is dangerously outdated with 42 security vulnerabilities waiting to be exploited. Every day your site runs this version, you risk unauthorized access, data theft, and complete website takeover. The fix is straightforward: update to a current WordPress version, update all plugins, and verify your site hasn't been compromised. The entire process typically takes less than an hour and provides essential protection for your business.

Don't leave your website exposed to cybercriminals. Use SiteRecipe.com's free security scanner to check your WordPress version, identify vulnerable plugins, and receive a customized action plan to secure your site. Our tool also monitors for malware and configuration issues that hackers exploit. Protect your website today—your customers and business data depend on it.

Frequently Asked Questions

Is WordPress 5.1.1 still receiving security updates?
No, WordPress 5.1.1 reached end-of-life years ago and no longer receives security patches from the WordPress development team. This means new vulnerabilities discovered in this version will never be patched, making it increasingly dangerous to use.
Can I be hacked just by running WordPress 5.1.1?
Yes, the 3 critical and 9 high-severity vulnerabilities in WordPress 5.1.1 can be exploited without any action from you. Hackers use automated tools to scan the internet for vulnerable WordPress versions and attack them 24/7. Running this version is essentially inviting attackers into your site.
Will updating to the latest WordPress version break my website?
Most updates are backwards-compatible, but outdated plugins may cause issues. Before updating, use SiteRecipe.com to identify problematic plugins, then update WordPress gradually. Test on a staging environment first if you have mission-critical functionality.
What happens if my site was already hacked through these vulnerabilities?
Use SiteRecipe.com to run a comprehensive malware scan immediately. You may have backdoors or stolen data that need professional cleanup. After updating WordPress, change all passwords and enable two-factor authentication to prevent future unauthorized access.

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DISCLAIMER: This report is based on publicly available CVE data from the National Vulnerability Database (NVD) maintained by NIST. Detection of a technology version does not confirm active exploitation on any specific website. For informational purposes only. SiteRecipe is not responsible for actions taken based on this report. Always consult a qualified security professional.

Source: nvd.nist.gov · Published: May 31, 2026 · SiteRecipe.com