Final answer:
The neglected upload of a password file by network security expert Sam poses a significant security issue related to password visibility, Option C.
Step-by-step explanation:
The security issue that arises from Sam neglecting to upload the password file revolves around password visibility. Without the password file, it is likely that the system lacks an essential layer of security to protect and encode user passwords, which means that passwords may be stored or transmitted in clear text. This is a significant security risk as unauthorized individuals could potentially intercept or access these passwords without needing to bypass any form of encryption, thus compromising user accounts and the integrity of the network.
When discussing network security, password visibility is a critical aspect because it pertains to how passwords are managed, handled, and stored within the system. Storing passwords securely often involves methods such as password hashing, which securely encrypts passwords and is a standard security measure that should be implemented. However, in the scenario where the password file has not been uploaded, this process can't take place, defaulting to a scenario where passwords may not be hashed and are left exposed.