Password managers less secure than promised

> IMPACT. Complete compromise of vault confidentiality and integrity. The adversary can read and decrypt all vault con- tents encrypted after the attack, including passwords, credit card information, secure notes, and other sensitive data stored in the vault. Similarly, they can inject new items into the vault after the attack. REQUIREMENTS. The client fetches key material from the server, for example due to the user logging in on a new device. If executed on a non-empty vault, the attack results in the client losing access to all items already in their vault, while leaking any new items added to the vault after the attack took place. If the attack is executed at the time of vault creation, the attack is effectively undetectable by the client, since it cannot distinguish between a ciphertext it created and the ciphertext created by the server during the attack. PROPOSED MITIGATION. A straightforward mitigation is to have the client sign vault keys using the RSA private key in the keyset before encrypting them with the RSA public key. Ideally, two different key pairs would be used for...

from the paper: https://eprint.iacr.org/2026/058.pdf

> We examine the extent to which security against a fully malicious server holds true for three leading vendors who make the Zero Knowledge Encryption claim: Bitwarden, LastPass and Dashlane [...] The attacks range in severity, from integrity violations of targeted user vaults to the complete compromise of all the vaults associated with an organisation.

Second: The provider can get the passwords with a simple server change.

It's not centralized, of course; you still have to download the entire database, and then potentially upload the entire database again for any changes; but it doesn't have these vulnerabilities.