Web applications, such as self-service customer portals provide efficiency, accessibility, and convenience, allowing customers to interact with services seamlessly. However, these same applications can become entry points for attackers if not properly secured.
One of the most overlooked yet critical vulnerabilities? File Upload Vulnerabilities.
Many web applications allow users to upload documents, images such as profile pictures, invoices, resumes, etc. But if file uploads are not secured properly, attackers can exploit them to execute malicious code, compromise servers, or gain unauthorized access to sensitive data.
One common mistake in web applications is relying on client-side validation to restrict file types.
For example, a web app might allow only .jpg and .png image uploads. However, this restriction is often enforced only in the browser. An attacker can easily bypass this using interception tools like Burp Suite or OWASP ZAP by:
Uploading a malicious script (e.g., a PHP or ASPX web shell).
Intercepting the request before it reaches the server.
Modifying the file extension or content type to disguise the payload.
Successfully uploading and executing the file, leading to full server compromise especially via Remote Code Execution (RCE) where attackers upload a backdoor script and gain full control of the server.