The fact that website URLs are in plaintext means that a successful decryption of the master password could give the attackers a sense of the websites a particular user holds accounts with, enabling them to mount additional phishing or credential theft attacks. 'If you reuse your master password and that password was ever compromised, a threat actor may use dumps of compromised credentials that are already available on the internet to attempt to access your account,' LastPass cautioned. Join our webinar and learn how to stop ransomware attacks in their tracks with real-time MFA and service account protection. Learn to Stop Ransomware with Real-Time Protection It bears noting at this stage that the success of the brute-force attacks to predict the master passwords is inversely proportional to their strength, meaning the easier it is to guess the password, the lesser the number of attempts required to crack it. The company did not divulge how recent the backup was, but warned that the threat actor 'may attempt to use brute-force to guess your master password and decrypt the copies of vault data they took,' as well as target customers with social engineering and credential stuffing attacks. LastPass confirmed that the security lapse did not involve access to unencrypted credit card data, as this information was not archived in the cloud storage container. These fields, the company explained, are protected using 256-bit AES encryption and can be decoded only with a key derived from the users' master password on the users' devices.

It's stored in a 'proprietary binary format' that contains both unencrypted data, such as website URLs, and fully-encrypted fields like website usernames and passwords, secure notes, and form-filled data. On top of that, the adversary is said to have copied customer vault data from the encrypted storage service.

LastPass said this permitted the unidentified attacker to obtain credentials and keys that were subsequently leveraged to extract information from a backup stored in a cloud-based storage service, which it emphasized is physically separate from its production environment.

Last pass data breach