When updating any system starting July 4, you will receive a security warning explaining a CVE found in Calamares, the system installer used in KaOS.
The warning includes an explanation what is found and what to do to improve the security of your password(s).

Should you have any questions for this, please ask in this thread. Should you have clicked the message away too soon and like to read it again, it is available at /usr/share/kde-common/system.md, best read it with a markdown reader like cutemarked:

cutemarked /usr/share/kde-common/system.md

(install cutemarked if you'd like to use it, not part of a default KaOS install)
Or just use kdialog:

kdialog --textbox /usr/share/kde-common/system.md 900 600

You can also read about the CVE at the Calamares website:
https://calamares.io/calamares-cve/