WP_Query is the WordPress core class used to build content queries. It lets the platform, plugins, and themes retrieve posts, pages, and other content using structured arguments such as author, category, search terms, and ordering rules. In normal use, it is the standard way WordPress turns high-level filters into database lookups.
From a security perspective, WP_Query matters because it sits at a trust boundary. If a plugin or theme passes raw request data into query arguments without validation, attacker-controlled values can affect how the application builds SQL. That can create opportunities for SQL injection, data exposure, or abusive filtering behavior. Defenders reduce this risk by treating all input as untrusted, casting values to expected types, using allowlists for query parameters, and updating WordPress core. When custom database access is needed, parameterized queries remain the safer pattern because they keep code and data separate.