A critical integrity and security warning for altering the structure of the WordPress core option _user_roles

At the heart of the WordPress roles & capabilities system is the WordPress core option _user_roles. While customizing user roles and their capabilities is encouraged for site-specific needs, altering the underlying data structure of the _user_roles option is a different matter entirely. Changing the structure of this serialized array can have catastrophic consequences for your website’s security, stability, and overall functionality.

This article will explain why it's safe to modify user roles and capabilities within the existing structure, but why altering the core data structure of _user_roles is a dangerous practice that should be avoided at all costs.

# What is the _user_roles option?

The _user_roles option is a serialized array stored in your WordPress database under the wp_options table. It defines the roles within the system (e.g., "Administrator", "Editor", "Author") and their associated capabilities (e.g., the ability to publish posts, edit themes, or manage plugins). Each role is an entry in the array, and each entry contains a list of capabilities.

Here’s a simplified example of what the _user_roles array might look like in your database:

{
   "administrator": {
      "name": "Administrator",
      "capabilities": {
         "manage_options": true,
         "edit_posts": true,
         "delete_posts": true,
         // More capabilities
      }
   },
   "editor": {
      "name": "Editor",
      "capabilities": {
         "edit_posts": true,
         "publish_posts": true,
         "delete_posts": true,
         // More capabilities
      }
   }
   // Other roles...
}

The structure of this array is carefully designed by WordPress to maintain consistency, security, and functionality across the site and its plugins. While you can safely add, remove, or modify roles and capabilities within this structure, altering the structure itself can lead to severe problems.

# Why altering the array structure is risky?

These are just a few reasons why altering the data structure for the _user_roles option is dangerous and should be avoided:

1. Incompatibility with Core Functions. WordPress’s core functions expect the _user_roles array to be in a specific format. When you change the underlying structure (such as adding new keys, removing essential ones, or nesting data differently), you disrupt this expectation. This can break key WordPress functionalities like user management, content publishing, and plugin handling.

   For example, functions like current_user_can()open in new window, which checks if a user has the required capability to perform an action, rely on the proper structure of the _user_roles array. A deviation from the expected structure can result in this function failing, either denying legitimate users access or, worse, granting unauthorized access.

2. Plugin and Theme Conflicts. Many plugins and themes rely on the role and capability system to grant or restrict access to certain features. These add-ons use core WordPress functions that interact with the _user_roles array in its default structure. If the structure is altered, plugins may not be able to correctly interpret user roles, leading to unpredictable behavior.

   Imagine a security plugin that checks for admin-level capabilities to perform sensitive actions. If the array structure has been changed, it may not correctly identify whether a user has administrative privileges, allowing unauthorized actions to be performed or restricting legitimate access.

3. Serialization Issues. The _user_roles option is stored in the database as a serialized array, meaning it is converted into a string format that can be saved in the database and later re-converted into an array when retrieved. If the structure of the array is altered in a way that breaks the serialization process, WordPress may fail to unserialize the array properly, resulting in a corrupted role system. This could lock out all users or cause a complete breakdown in role-based access control.

   Serialization is fragile: even small errors, like changing the nesting depth of an array or altering data types (e.g., converting a boolean to an integer), can lead to unserialization failures.

4. Security Vulnerabilities. The integrity of _user_roles is critical for the security of your WordPress installation. Altering the array structure can introduce vulnerabilities by inadvertently removing or modifying security-critical capabilities. For instance, if you modify how roles are stored or processed, attackers could exploit these changes to bypass access controls, elevate privileges, or even inject malicious code.

   WordPress roles are part of the Role-Based Access Control (RBAC) system, which enforces restrictions based on user roles. If the structure is compromised, this enforcement can break down, leaving your site open to privilege escalation attacks.

5. Breaking Future Updates. WordPress is continually updated to improve functionality and security. If you alter core elements like the structure of _user_roles, future updates may overwrite your changes, resulting in unpredictable behavior. Additionally, your changes may make it difficult for WordPress to correctly update its database schema or core functions, leading to conflicts and potential data loss.

# Conclusion

The _user_roles option is a cornerstone of WordPress’s role management system, and while modifying roles and capabilities is a common practice, altering the structure of this core option is highly discouraged. Doing so risks breaking WordPress’s core functionalities, causing plugin and theme conflicts, introducing security vulnerabilities, and even leading to site downtime due to serialization issues.

If you need to make changes to the roles and capabilities on your WordPress site, always use the provided APIs and built-in functions. These tools allow for safe and effective customization without compromising the integrity of your site’s role-based access control system. By keeping the structure of _user_roles intact, you maintain the security, stability, and proper functioning of your WordPress installation.