This feature is deprecated. If you use Windows 10, we recommend OpenSamEndpoint since version 0.7.0 / 5.48.0: #938
BlockPassword is a sandbox setting in Sandboxie Ini. It specifies whether Sandboxie will allow sandboxed programs to change the password of user accounts.
. . . [DefaultBox] BlockPassword=n
Specifying n indicates that a sandboxed program should be permitted to issue requests to change the user account password.
Related Sandboxie Control setting: Sandbox Settings > Restrictions > Low-Level Access