[{_id:123,url:"test.com?from_user=1",name:"Superhero"},{_id:124,url:"regex.com?from_user=3",name:"Journalist"},{_id:125,url:"test.com?from_user=2",name:"Software Developer"}]

db.collection.update({"url":{"$regex":"test.com"}},[{"$set":{"url":{"$replaceAll":{"input":"$url","find":"test.com","replacement":"example.com"}}}}],{"multi":true})