AES is used by the US government and other government agencies around the world for protecting top secret data. With proper implementation and a strong encryption key (your master password), AES is considered unbreakable.
PBKDF2 is used to derive the encryption key from your master password. This key is then salted and hashed.
bitwarden does not write any crypto code. bitwarden only invokes crypto from popular and reputable crypto libraries that are written and maintined by cryptography experts. The following crypto libraries are used:
bitwarden always encrypts and/or hashes your data on your local device before it is every sent to the cloud servers for syncing. The bitwarden servers are only used for storing encrypted data. It is not possible to get your unencrypted data from the bitwarden cloud servers.