This is an XML External Entity (XXE) attack, which occurs when an application processes XML input that allows external entity references. The best mitigation is to disable external entities in the XML parser.
* Option A (Change file permissions) #: Changing file permissions does not fix the root cause, as the vulnerability is in XML processing.
* Option B (Review logs) #: Logs help with detection, but do not prevent XXE attacks.
* Option C (Disable external entities) #: Correct.
* Disabling external entity resolution in the XML parser prevents XXE attacks.
* Option D (WAF) #: A WAF can help block attacks, but disabling external entities is the best solution.
# Reference: CompTIA PenTest+ PT0-003 Official Guide - Web Application Attacks (XXE)