6 Web Application Vulnerabilities and How to Prevent Them

One of the biggest fears for development managers is not identifying a vulnerability in their web application before an attacker finds it. Web application vulnerabilities leave you susceptible to security attacks during which valuable customer and company data could be at risk. As a result, you will incur huge financial losses while your reputation suffers serious damage.

The good news is that these web application security threats are preventable. roper knowledge of the most common web application vulnerabilities is the key to prevention. While you may conduct automated scans and regularly test for any web application vulnerabilities, those efforts will be in vain unless you know what to look for.

This makes it crucial to understand web security vulnerabilities inside out – right from how a web application gets targeted to what kind of vulnerabilities to look for and how to prevent them. This post is going to help you do exactly that.

How Web Application Vulnerabilities Affect Companies

First, let’s try to gain a better understanding of how exactly these website application vulnerabilities can affect a company. This will help you understand just how harmful these security attacks can be and why you should prioritize preventing them.

One of the biggest, most harmful web application security threats is sensitive data exposure. It even ranks among the OWASP top 10 vulnerabilities. It involves compromising important data that should have been protected. This includes data like passwords, credentials, personally identifiable information, social security numbers, credit card numbers, health information, etc.

This is one of the most targeted web application vulnerabilities by hackers since there’s a prospect for financial gain for them. They could sell this data or use it themselves to conduct fraud, identity theft, etc.

There are tons of ways for hackers to steal sensitive data through web security vulnerabilities:

  • They may look for  SQL injection flaws to retrieve decrypted credit card numbers.
  • They could exploit insecure wireless networks to seal a user’s session cookie.
  • Attackers could even retrieve sensitive files from the server using a file download vulnerability, or upload malicious files to target your users!

In some cases, you may even encounter Cross-Site Scripting (XSS). This is one of the most widespread website application vulnerabilities and involves utilizing the website as a propagation method. Hackers would inject malicious client-side scripts and modify how the website functions or how it is displayed.

An XSS attack could infect your visitors’ devices with malware or have them recruited into large botnets. It could mislead your visitors and damage your credibility and reputation, which can be extremely difficult to rebuild.

These are just a few ways in which hackers can exploit web application vulnerabilities and cause serious harm to your company and its customers. But even from this, you can clearly see just how damaging these attacks can be and how crucial it is to prevent them. We need to take web application security threats seriously and turn our development teams into security champions.

Understanding the Common Web Application Vulnerabilities

Now let’s take a look at some of the most common attacks that hackers might attempt on your website. Knowing these common web application vulnerabilities will help you identify them faster and fix them more easily.

1: SQL Injection

Many hackers start with an attempt to gain access to the database through SQL injection attacks. This is when the attacker inserts malicious SQL statements into form fields and other injection points, with the intention of gathering information from and controlling the database. They can use this information to access and modify or even destroy the information, and to attack the underlying system.

Attackers typically use these attacks to collect vital customer information such as their contact information, passwords, or even credit card info. They may even exploit these web security vulnerabilities to change the price of a product, for instance. Advanced attacks can even allow them to control the database server and the operating system.

How to Prevent It

  1. Prepared statements with parameterized queries can mitigate SQL-related web application vulnerabilities. A prepared statement helps to sanitize the input and ensures that it is considered as a string literal in SQL rather than as part of the SQL query. In other words, the database can tell the difference between SQL data and SQL code. So the code is no longer vulnerable to SQL injection attacks as the query is less vulnerable to tampering.
  2. Migrating to Object Relational Mapping Tools (ORMs) is another excellent option. However, most ORMs allow non-parameterized queries in addition to performing parameterized queries. As such, it’s crucial to carefully use the frameworks keeping this in mind.
  3. Make the most of LIMIT and other SQL controls within your queries so that even if an SQL injection attack does occur, it can prevent the mass disclosure of records.

2: Cross-Site Scripting (XSS)

As mentioned earlier, cross-site scripting or XSS is one of the most popular web application vulnerabilities that could put your users’ security at risk. These attacks inject malicious code into the running application and executes it on the client-side.

The goal of XSS attacks is to send this malicious code to other users, sometimes infecting their devices with malware or stealing sensitive information. This type of website application vulnerability can give the attacker full control of the user’s browser and can be extremely dangerous to any website.

How to Prevent It

  1. Modern frameworks have made it a lot easier to escape untrusted user input and mitigate XSS attacks. AngularJS, React JS, and Ruby on Rails are some of the latest, most effective frameworks to prevent these web application vulnerabilities. These frameworks can automatically escape user input and help mitigate XSS attacks by design, although they do have limitations.
  2. Avoid implementing a blacklist,  instead favor of a whitelist, because blacklists are less effective at preventing web security vulnerabilities. An attacker who knows what they’re doing can easily bypass a blacklist filter.
  3. The ultimate solution to prevent these web application vulnerabilities is output encoding. This involves converting untrusted user input into a safe form so the input is displayed to the user as data without being executed as code in the browser. This means that special characters will be translated into an equivalent form that the browser will no longer find significant.
  4. It’s also important to understand that output encoding depends on the context of where data is being output. For instance, you may have HTML contexts, HTML entity contexts, HTML attribute contexts, CSS contexts, JavaScript contexts, and more. As such, you will need to apply context-sensitive encoding when render the page for the browser.
  5. Enable a Content Security Policy (CSP), which can be very effective to help mitigate Cross-Site Scripting vulnerabilities.

3: Authentication Failure

Authentication-related web application vulnerabilities occur when there’s an improper implementation of adequate user authentication controls. This puts user accounts at risk of being breached. Attackers may exploit these web security vulnerabilities to gain control over any user account or even over the entire system.

One of these vulnerabilities is Credential Stuffing, where an attacker will test a list of valid passwords and usernames gleaned from another breach or attack until they manage to find a valid combination and gain access.

Another common vulnerability is a Brute Force attack, in which the attacker tries every possible character combination until they find a valid one.

Session hijacking is another common attack that can occur as a result of authentication failure. This is when there is a failure to properly invalidate session IDs, allowing attackers to exploit an authenticated session of a legitimate user.

How to Prevent It

  1. One of the essential steps to avoid these web application vulnerabilities is to allow enough time for developers to test the code before it gets deployed to production. External security audits can also help ensure that you apply the best practices of website security.
  2. Avoid deploying with default credentials, especially for admins.
  3. Wherever possible, make sure you implement multi-factor authentication to make your system less vulnerable to the attacks mentioned above.
  4. Put a limitation or delay on failed login attempts. Make sure you log all failures and notify administrators when there’s an attack attempt.
  5. Avoid unnecessarily restricting input size. If you allow more characters, there are fewer chances for attackers to guess the right password.
  6. Have some form of lockout in place to prevent brute force attacks and minimize these web application vulnerabilities.
  7. Use adaptive hashing algorithms like bcrypt, pbkdf2, argon2, etc. to salt passwords and hash them before storing them in the database
  8. Implement weak-password checks for better password security. This would include testing new or changed passwords and comparing them against a list of compromised or weak passwords. Use of a service to check for compromised passwords (such as Have I Been Pwned) helps to automate this functionality and keeps the list of compromised passwords up to date as new attacks occur.

4: Security Misconfiguration

Security misconfigurations provide attackers with an easy way into your website, making it one of the most critical web application vulnerabilities that you need to prevent.

Unused pages, unpatched flaws, unprotected files and directories, and default configurations, are some of the security misconfigurations that attackers can leverage to gain unauthorized access.

Every level of your application stack can be vulnerable to security misconfigurations. This includes your web server, platform, database, network services, storage, frameworks, application server, and more.

If attackers manage to exploit these web application vulnerabilities, they can access sensitive information and take control of user and admin accounts.

How to Prevent It

  1. Make sure you use encrypted (HTTPS) connections to transfer data and information between the users and the application.
  2. Have a repeatable hardening process that you can quickly and easily deploy on another environment. This will save time in setting up a new and secure environment as you’ll be able to automate the process.
  3. Perform all remote admin tasks through secured channels to minimize these web application vulnerabilities. Even if you do have to use protocols that don’t support strong encryption, make sure you activate them over a secondary encryption channel such as IPSEC, or TLS.
  4. Regularly conduct file integrity checking to ensure that there haven’t been any unauthorized changes to critical files. Use file integrity checking tools that can accept routine and expected changes while alerting you of any unexpected or unusual changes.
  5. Have an automated process in place to regularly verify the effectiveness of your settings and configurations in every environment. You can use an automated configuration monitoring tool that can alert you of any unauthorized changes. This will help you identify these web application vulnerabilities before they cause any damage.
  6. Keep your platform minimal and avoid adding unnecessary features, samples, documentation, and components. If you have unused features and frameworks in the platform, it’s best to remove them to prevent web application vulnerabilities.

5: XML External Entities

An XML external entity attack, also known as an XXE, or an XML injection attack, is another class of vulnerabilities you should watch out for. These types of attacks occur when attackers exploit a weakly-configured XML parser. Through such attacks, attackers can inject additional data, access confidential data, and execute applications and create remote tunnels (shells).

XML external entity attacks can also result in remote code execution, Server Side Request Forgery (SSRF), and more. By default, most XML parsers are prone to these attacks. This leaves it up to the developers to ensure that their web application is free from these web application vulnerabilities.

How to Prevent It

  1. Completely disabling Document Type Definitions (DTD’s), also known as External Entities, is the safest way to prevent XXE attacks. This secures the parser against DoS attacks. However, it may not always be possible to completely disable DTDs. In this case, you need to disable external document type declarations and external entities in a specific way for each parser.
  2. Whenever possible, you should try using less complex data formats like JSON. It’s also good to avoid serialization of sensitive data to avoid these website application vulnerabilities.
  3. Implement a positive, server-side method to validate, sanitize, and filter input. This will help prevent the occurrence of hostile data within your XML documents, nodes, and/or headers and help you avoid XXE-related web application vulnerabilities.
  4. Patch or upgrade all the XML processors and libraries that the application or its underlying OS is using.
  5. While the best solution is to use manual code review for critical functionality in large and complex applications, you should also use SAST tools to detect XXE in source code.
  6. Use XSD validation or an equivalent alternative to validate the incoming XML structure.

6: Broken Access Control (Authorization Failure)

Access control helps you control what sections of a website and what application data different visitors can access.

For instance, if your website is a platform for different sellers to list their products, they will need some kind of access to add new products and manage their sales. However, not every visitor will need that level of access since most of them are visiting your site to buy products.

As such, having a broken access control opens up your site to web application vulnerabilities, which attackers can exploit to access sensitive information or unauthorized functionality. They might even use these attacks to make modifications to access rights and user data.

How to Prevent It

  1. It’s crucial to maintain a security-first policy when developing and configuring software.
  2. Except for public resources, deny access by default.
  3. Make sure you apply protection horizontally (across all data) and vertically (across all levels of access privileges). Vertical protection involves employing the least privilege concept wherein access is granted only in accordance to their
  4. Centralize all authorization decisions to minimize the occurrence of access-related web application vulnerabilities.
  5. Instead of letting users freely create, read, modify, or delete any record, use model access controls to enforce record ownership. Remove their ability to read or modify data from other users.
  6. Implement a one-time access control mechanism that you can reuse through the 1.
  7. Set limitations to API and controller access to reduce the risk of attacks by automated tools.
  8. Invalidate JWT tokens and user sessions on the server after logout.
  9. Disable webserver directory listing and also prevent web roots from storing backup files and file metadata.

Final Thoughts

These are some of the most common web application vulnerabilities that you should watch out for and try to prevent. Doing so will help you avoid a large number of web application security threats.

Combined with your regular tests and automated scans, you should be able to utilize this list to minimize the risk of security threats and ensure better security of sensitive information.

However, it’s important to note that these aren’t the only vulnerabilities you should be aware of. There are plenty of other harmful web application vulnerabilities such as insecure cryptography, insufficient logging and monitoring, and using components with known vulnerabilities.

Being aware of all of them will help you enhance security and protect valuable data against security threats.


Cypress Data Defense was founded in 2013 and is headquartered in Denver, Colorado with offices across the United States. Our goal is to help organizations secure their IT development and operations using a pragmatic, risk-based approach. The diverse background of our founders allows us to apply security controls to governance, networks, and applications across the enterprise.

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