Definition
XXE or XML external entity is a type of web application vulnerability that occurs when an attacker can interfere with the parsing of XML data. This interference allows the attacker to access sensitive files on the server, execute commands, or perform denial of service attacks. The vulnerability arises when an XML parser is configured to process external entities, which can point to arbitrary files or URLs. Understanding XXE is crucial for securing web applications and preventing data breaches. For instance, an attacker might exploit an XXE vulnerability in a file upload feature to read a server's configuration files. It is distinct from SQL injection, which targets database queries rather than XML parsing. This topic is frequently covered in cybersecurity certifications like CompTIA Security+ and CISSP.