Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment. Prior to 6.13.9, 7.8.9, 8.22.1, and 9.1.6, a vulnerability allows bypassing Mongoose’s sanitizeFilter query sanitization mechanism via the $nor operator. When sanitizeFilter is enabled, Mongoose wraps query operators in $eq to neutralize them. However, prior to the fix, $nor was not included in the set of logical operators that are recursively sanitized. Because $nor accepts an array (like $and and $or), and arrays do not trigger hasDollarKeys(), malicious operators such as $ne, $gt, or $regex could be injected inside a $nor clause without being sanitized. This vulnerability is fixed in 6.13.9, 7.8.9, 8.22.1, and 9.1.6.