Database
[{_id:ObjectId("63cc5b1ba37b898e16d3f4f6"),username:"a",email:"b",cars:[{_id:ObjectId("63cc5b1ba37b898e16d3f4f7")},{_id:ObjectId("63cc5b1ba37b898e16d3f4f8")}],},{_id:ObjectId("63cc5b1ba37b898e16d3f4f9"),username:"c",email:"d",cars:[{_id:ObjectId("63cc5b1ba37b898e16d3f4fa")},{_id:ObjectId("63cc5b1ba37b898e16d3f4fb")}],},]
Query
db.collection.update({username:"a"},{$set:{"cars.$[item].size":"large","cars.$[item].color":"blue"}},{arrayFilters:[{"item._id":ObjectId("63cc5b1ba37b898e16d3f4f7")}]})