Software Development Updates

Many websites and web applications on the internet are powered by PHP.  Its versatility, dynamic nature, large active community, ease of use, and vast ecosystem make it a go-to option for many web developers. PHP development, if done right, can provide several benefits. However, being careless during programming may give way to some serious PHP vulnerabilities. If these vulnerabilities are not addressed, your web applications may become exposed to various security risks, providing an opportunity for attackers to steal your data or disrupt the app workflow. 

You can easily mitigate these vulnerabilities with the help of a reliable PHP development company. But before that, you must understand PHP vulnerabilities. 

Therefore, this blog explores different types of PHP vulnerabilities and discusses how to solve them. As an added benefit, we also offer a few tips for secure PHP web app development. So, let’s get started.

1. What is a PHP Vulnerability?

A weakness or an issue in your PHP program can be defined as a PHP vulnerability. There are different kinds of PHP vulnerabilities; some may be small, leading to minor code flaws, whereas some are big enough to cause system failures.

Having these vulnerabilities also poses significant security risks, as they can be used to exploit or gain unauthorized access to your PHP application to steal data or carry out malicious activities. 

It is important to understand the PHP vulnerabilities so you can eliminate them from your system. Some of the most common vulnerabilities seen in a PHP app are file inclusion vulnerabilities, code execution, cross-site scripting, and SQL injection.

2. Severe PHP Vulnerabilities and How to Fix Them?

When a PHP program is written in a careless and untidy manner, it leaves gaps for PHP vulnerabilities. Following that, your code wouldn’t work up to expectations and is left for easy exploitation. In this section, we will discuss some major PHP vulnerabilities and how you can prevent or fix them.

2.1 Cross-Site Scripting (XSS)

Cross-site scripting (XSS) occurs when an attacker plants a script on your website to perform malicious actions like granting unauthorized access, stealing cookies, or manipulating data whenever a user visits your website. 

Let’s say your website has a message board where users can leave messages. However, without a validation process in place, any unauthorized visitor can leave a message or plant malicious code on your website. This will expose the visitors to a malicious script that might be designed to steal login credentials or other confidential data. 

In short, XSS is a PHP vulnerability that occurs when your website accepts user-supplied data without proper encoding. It is a client-side vulnerability targeting app users to steal their information.

How to Fix It?

• All the user inputs must be sanitized properly so that the app would see it only as data and not as a script.
• Implement a Web Application Firewall (WAF) to block potential malicious scripts. It ensures that no code is executed on your website without your permission. 
• Put a cross-scripting filter on your browser with the help of an XSS protection header. It will automatically detect an XSS attack and sanitize the web pages. 
• Using the HttpOnly flag helps by enabling the browser to return an empty string every time a client-side script tries to steal the cookie. 
• Use Content Security Policies (CSPs) to prevent the loading of malicious scripts on any of your web pages. 
• Always encode your output data using suitable encoding functions. It prevents the execution of any interpreted JavaScript or HTML code in your browser.

2.2 SQL Injection

SQL Injection is a PHP vulnerability where the attacker manipulates user input to inject malicious SQL code into your app’s database query. It allows them to easily steal or manipulate sensitive information such as passwords, financial details, and private data from your app’s database. In some cases, hackers also leverage the SQL injection attack to gain access to your entire website. 

Let’s see on Twitter what people are discussing about the SQL Injection:

SQL injection is a technique that allows attackers to access your web app’s backend database. This enables them to modify the privileges. If the SQL server is running as system admin, the attacker would have complete control of the server. 

How to Fix It?

• Utilize sanitization techniques to remove the special characters from user input. As a result, the system sees the malicious input as strings and never executes it. 
• Define the SQL query and relevant parameters to safeguard against SQL injection attacks. So, whenever an attacker tries to inject a malicious SQL script, the server will reject it immediately. 
• Utilizing PDO-prepared statements for database interactions, you can bind user inputs to the SQL queries before executing them. This method uses placeholders in the SQL queries for input, your system can easily tell the difference between the user inputs and predefined SQL queries.
• Old technological resources and programming languages didn’t have any features to prevent SQL injection attacks. Therefore, it is essential to use the latest technologies. Additionally, you can further add your layers of security on top of the SQL protection provided by these modern technologies.

2.3 Cross-Site Request Forgery (CSRF)

In Cross-Site Request Forgery (CSRF), attackers often use phishing tactics to make you believe that you logged into your secure website with proper authentication. In this attack, they craft specific links designed to either steal session information or automatically send legitimate commands to the server on your behalf. 

For example, when an attacker gets a site administrator or someone with high privileges to click a malicious link. Once the link is clicked, the attacker can create a new admin user with a password only they know. In this CSRF attack, the attacker needs the site admin to click on the link, and they get control of the entire website. 

How to Fix It? 

• Using authentication tokens is the best step to prevent CSRF attacks. It generates a new token for every new login action, which makes it difficult for hackers to take any unauthorized actions. 
• Expire valid sessions after a while to reduce the risks of CSRF attacks. 
• To enhance security, ensure that all cookies are sent in the first-party context only by setting the cookie’s SameSite attribute to “strict”. 
• Add an extra layer of security or consider re-authentication for sensitive user sessions or actions. 
• Implement the Custom header protection technique. It adds a servlet filter for checking all the requests for changing the valid CSRF token’s state.

2.4 Remote Code Execution (RCE)

In Remote Code Execution (RCE), the attackers can execute arbitrary PHP code directly on the server. They run their code remotely through the internet and execute code without being in the same physical space or using the same device. This trait differentiates RCE from arbitrary code execution, which needs to be launched from the system’s LAN. 

Remote code execution can occur when external attackers exploit vulnerabilities in your PHP web application. This often happens due to a failure to validate the user input or run unsensitized shell commands. The hackers take advantage of this opportunity and compromise your server’s PHP security by running malicious code. The hackers exploit RCE vulnerability in your PHP app to disrupt operations, steal sensitive information, or launch further attacks.

How to Fix It? 

• Avoid using dangerous functions like system() and eval(). 
• Always sanitize and validate the user-supplied input before you insert it in your PHP code. 
• Implement a robust authentication process along with strong access protocols. 
• Restrict access permissions and prevent unauthorized code execution. 
• Set up web application firewalls. 
• Use prepared statements or parameterized queries during database interactions.

2.5 Session Hijacking

The website creates a new session every time a user logs in. This approach prevents the need to request authentication for every subsequent action the user takes and maintains their logged-in status. The hackers can obtain information regarding the current session through CSRF and XSS attacks. 

Attackers can copy the user’s session ID and gain access to the web application or database. This happens when you allow users to start a session on your website without any prior authentication process.

The attacker also uses the man-in-the-middle attack to either hijack the legitimate user’s session or intercept its conversation with the server.

How to Fix It? 

• Generate a unique session ID for each login. Change them along with the privilege level once the user is authenticated. 
• Implement secure session management techniques like configuring session options and using the HttpOnly flag. 
• Ensure that cookies expire after a user logs out from the session and generate a new cookie for every login. 
• Data transmissions and communications between the client-side browser and web server must be properly encrypted. 
• Encrypt the session data, especially the ones with sensitive information, and store them on the server. Add an extra layer of PHP security when accessing this data. 
• Don’t just rely on session identifiers. Also, use a token-based authentication system. 

2.6 File Inclusion Vulnerability

A File Inclusion vulnerability is commonly seen during PHP projects. It occurs when the app allows users to add external files through user-supplied inputs. This seemingly small mistake allows the hackers to easily bypass implemented security restrictions to upload an arbitrary file to the system which grants them unauthorized access. 

Web apps depending on scripting runtime are highly affected by file inclusion vulnerabilities. Most of the poorly written apps are riddled with such PHP vulnerabilities. In this, the attacker can easily read and execute the server files remotely. 

How to Fix It? 

• The client-side validation can be easily bypassed. So you must also use server-side validation to make sure that the uploaded input has the correct file type. 
• Never use user-controlled inputs as a part of the file path, especially when implementing the require() or include() functions. If possible, always use absolute file paths. 
• Set a limit on the maximum file size. 
• Limit inclusion to secure directories that can only be accessed by privileged users. You can also use file permissions to restrict access to other directories. 
• Rename the uploaded files so the hackers can’t easily find the files to manipulate them. 
• Mitigate security risks by storing and serving uploaded files using a content delivery network.

3. Best Practices for Secure PHP Development

Implementing PHP security best practices ensures the safety of your PHP web applications and sensitive user data. In this section, we are going to discuss a few practices to help you prevent PHP vulnerabilities. 

3.1 Always Use the Latest Version of PHP

Every new version of PHP comes with new security updates and fixes for known vulnerabilities. Using older PHP versions would expose your app to various risks. So, it is recommended to use the latest version for PHP development. 

Regularly check the PHP-supported versions page to see if your installations are up to date on the latest PHP offerings. This helps you take proactive measures against potential security breaches and data leaks. As a result, the overall security and resiliency of your web apps will increase.

3.2 Secure File Uploads

If your file uploading process does not have a proper validation mechanism, it can pose significant risks to your system and its data. This is a common point of vulnerability that needs to be secured using PHP best practices. Ensure that you validate the file type, limit the file size, and ensure the upload happens from a secure location. 

In addition to client-side validation, perform a server-side validation to enhance security. Scan and sanitize all the files before uploading them to prevent the execution of any malicious code. Furthermore, restrict direct access to the uploaded files by storing them outside the web root directory. 

3.3 Use HTTPS

Use HTTPS protocol across your web application to encrypt data transmissions between the web server and the user’s browser. It is to ensure that your data and communications are secure from man-in-the-middle attacks. 

Just by adding a few lines of code in your .htaccess file, you can also enforce a redirection from HTTP to HTTPS in a PHP system. This will help secure your website using TLS or SSL techniques for encryption. 

Obtaining an SSL certificate from a trusted authority and configuring your web server to support HTTPS is one of the most important best practices to secure PHP web applications. It helps improve your site’s security, increases its credibility, and improves its visibility at the top of search results. 

3.4 Educate and Train All Employees

Ensure that all the employees in your company are aware of common security threats. So they don’t get lured into phishing or other cyberattacks. Inform them to create strong passwords and use them properly. You can also put a multi-factor authentication process in the application. 

Also, train your developers to implement PHP security best practices when writing the app code. Keeping them updated on the latest trends and technologies is not enough. They also need to learn how to overcome the limitations of these new technologies. After all, that’s what hackers choose to exploit the most. 

Along with the regular security training, make sure you also provide them with detailed documentation on how to keep your code and app secure. They must know how the PHP code and app work, as well as their vulnerabilities. Otherwise, how are they going to mitigate them?

3.5 Do Not Store Passwords

Don’t be careless with your passwords, and store them as plain text. If you need to store the password, then use some robust one-way hashing algorithms like bcrypt to change it into a string of unique characters. 

This will make it challenging to retrieve the original password. Securely saving your password is necessary as it acts as another layer of protection for user credentials to prevent any unauthorized access to the app or its database. 

4. Conclusion

PHP is one of the most widely used programming languages for web app development, making it an easy target for hackers. So, it is important to ensure that there isn’t any vulnerability in your PHP code. In this article, we discussed some of the most common PHP vulnerabilities, how to fix them, and the best security practices for web app development. 

Ensure that identifying and eliminating PHP vulnerabilities becomes a part of your development cycle. It helps enhance the security of your web applications. In the case of app security, you have to be proactive and eliminate all the potential threats and vulnerabilities.