If you want the absolute latest stock firmware (Version 3.74) directly from the source, copy and paste this official PlayStation network URL into your browser: http://playstation.net
The ConsoleMods integration pages host comprehensive guides for legacy systems, often linking to trusted GitHub repositories containing indexed MD5 hashes and download mirrors for every firmware version ever released. How to Install the Update File psp2updat pup download link
2. The Trusted Modding Archives (For Downgrading/Specific Versions) If you want the absolute latest stock firmware (Version 3