View-state is an ASP.NET mechanism that preserves a web page’s state between requests. Instead of rebuilding form values and control settings from scratch on every postback, the application stores that state in a hidden field and protects it with cryptographic validation, and sometimes encryption. When the page returns, the server checks that the data was not altered before using it.
In cyber security, view-state matters because it sits on the trust boundary between browser and server. If an attacker can steal the keys used to validate or decrypt it, they may forge or tamper with page state, sometimes turning a harmless web feature into a path for abuse or code execution. Defenders protect view-state by keeping machine keys secret, rotating them when exposure is suspected, and ensuring every server in a farm uses the same updated keys.