Hardware Devices, such as a Trezor or Ledger, periodically release firmware upgrades to their devices.
If you have not yet initialized your Hardware Device and added it to Casa App (formerly Keymaster), and don't have funds on it, you are safe to upgrade your firmware.
Once you've initialized your Hardware Device Key and added it to Casa App as part of your multisig setup, we recommend declining firmware upgrades to the device, even if you're prompted to upgrade.
The reason for not going forward with an update is that some firmware updates wipe the device and require the seed phrase backup to restore. Since our recommendation is that you not keep a copy of your device's seed phrase, you should decline firmware updates.
In addition, firmware upgrade may affect compatibility with adding signatures in the Casa Api.
If there is ever a critical firmware upgrade which affects the security of your device with Casa App, we will let our users know, along with the best next-steps.