n8n before 1.123.69, 2.33.4, and 2.34.1 contains a NoSQL injection vulnerability in the MongoDB node's Find, Delete, and Aggregate operations, which parse the Query parameter as JSON after expression resolution without sanitizing MongoDB operators. An attacker who can influence the resolved query (e.g., via externally-controlled data) can inject operators such as $ne or $where, turning an intended single-document lookup into full-collection disclosure, full-collection deletion, or other operations on the database server.