Database
[{"_id":"5ded1a559015155eb8295f48","password":"20EABE5D64B0E216796E834F52D61FD0B70332FC:2512537"}]
Query
db.collection.aggregate([{$addFields:{password:{$arrayElemAt:[{"$split":["$password",":"]},0]},popularity:{$arrayElemAt:[{"$split":["$password",":"]},1]}}}])