This question already has an answer here:
I want to know what are the best practices to secure
NoSql database like
MongoDB. How is it possible? Any tips?
For mongodb i have written this answer
First vulnerability similar to sql injection can be done in mongodb or nosql databases too. which would be mongodb injection.
Try to run mongodb on different port instead on default 27017 to avoid exposing. For official security practices you can always check out http://docs.mongodb.org/manual/administration/security/
It tell security practices that should be used with mongodb server.
Mongodb Injection :
its fully describes here for php how mongodb injection can take place in phpwebapp if client side data is not filtered properly. Also solution to mongodb injection too
Mongodb Null byte injection attack
This is also a type of attack that is well written on this site , Have a look how certain fields in mongo collection can be overwritten using this method can this can be done in any webapp.