The security implications of not having a read-only WordPress file system

One critical security concern that is often overlooked is the need to set the file system, especially sensitive directories such as /wp-content/plugins and /wp-content/themes, to read-only. The subject of /wp-content/uploads read-only folder is much larger and require a separate article, so here we are going to focus only on plugins and themes.

When the file system of a WordPress website is not set to read-only, it opens the door for hackers to modify the files, inject malicious code, or install backdoors, significantly increasing the risk of a website compromise. Here's why this security vulnerability matters, and how reputable hosting providers address it.

# Why the wp-content Directory is Critical

The wp-content directory is very important for any WordPress site. It houses essential files that make up your website’s themes and plugins, which in turn define the design and functionality of your site. Here’s a breakdown of key components that live in wp-content:

• wp-content/plugins: This folder contains all the plugins that extend the functionality of your WordPress site. Plugins range from simple SEO tools to complex e-commerce functionality.
• wp-content/themes: This folder stores your active theme and any other themes you've installed. Your theme defines your site's layout and design.

Because these directories contain executable PHP files, they are a prime target for malicious actors looking to exploit vulnerabilities. If a hacker gains access to these files and they are writable, they can alter them to inject malicious code, create new vulnerabilities, or disable key security mechanisms on your site.

# Security Risks of Writable Directories

When the file system of a WordPress site is not set to read-only, especially in critical folders like /wp-content/plugins and /wp-content/themes, it introduces several security risks:

1. Code Injection: Hackers can modify PHP files in the wp-content directory to inject malicious code such as malware, phishing scripts, or spammy links. This allows them to take over the site, steal sensitive user data, or use the compromised website to distribute malware to visitors.

2. Backdoors: Backdoors are hidden scripts that hackers leave behind to retain access to a compromised site even after the initial vulnerability has been fixed. Writable directories make it easier for hackers to plant backdoors, allowing them to return to the site later to exploit it further.

3. Theme or Plugin Tampering: If a hacker gains access to a theme or plugin file, they can modify the functionality or break the site entirely. For example, a malicious actor could change a plugin to send sensitive information, such as user passwords or payment details, to a third party.

4. Breaking Site Functionality: While hackers may have malicious intent, unintended consequences can occur from modifying theme and plugin files. A poorly written or malicious modification could crash the site, introduce errors, or render the website unusable.

5. SEO Damage and Blacklisting: Hackers often inject links to malicious or spammy websites into compromised WordPress sites, which can severely damage SEO rankings. Worse, if your site is found to be serving malware or spam, it could be blacklisted by Google and other search engines, causing significant loss of traffic and credibility.

# How Reputable WordPress Hosts Mitigate These Risks

Many reputable WordPress hosting providers have recognized the dangers associated with writable file systems. To mitigate the risks, they often implement the following security measures:

1. Locking Down File Editing: Hosting providers can disable the ability to edit files directly from the WordPress admin dashboard. This is done by setting the DISALLOW_FILE_EDIT constant to true in the wp-config.php file. This simple measure prevents anyone, including hackers, from modifying theme and plugin files via the WordPress dashboard.

2. Read-Only Permissions for Key Directories: Top-tier WordPress hosting providers often set the /wp-content/plugins and /wp-content/themes directories to read-only. This ensures that even if a hacker gains access to the file system, they cannot modify the critical executable files that power the site.

3. Automatic File Integrity Monitoring: Some hosting providers offer file integrity monitoring services, which alert administrators whenever changes are made to sensitive files. This allows for the quick detection of unauthorized modifications, enabling site owners to act before the damage escalates.

4. Version Control and Backups: Reputable hosts often maintain automatic backups and version control systems. If malicious code is introduced, administrators can quickly restore the site to a previous, uninfected state, minimizing downtime and loss.

5. Limited Access Controls: Limiting access to files through permissions (i.e., assigning correct read/write access only to necessary users or processes) and ensuring that users with administrative privileges use strong passwords and two-factor authentication is essential. Hosting providers often enforce these best practices to minimize the risk of compromised credentials leading to file system vulnerabilities.

# Conclusion

Leaving the WordPress file system, particularly directories like /wp-content/plugins and /wp-content/themes, writable can expose your website to severe security risks, including code injection, backdoors, and site functionality breaks. Reputable hosting providers mitigate these risks by enforcing read-only permissions and disabling file editing capabilities. As a WordPress site owner, it is essential to adopt these best practices to protect your site from becoming a target of malicious actors.

By securing your file system, you not only improve the security of your website but also protect the integrity of your business and the trust of your users.