How do you enforce SSL/certificate pinning in MAUI?

Validate the server certificate in the HttpClient handler by comparing its public key/thumbprint to a pinned value, rejecting mismatches. Configure via HttpClientHandler.ServerCertificateCustomValidationCallback (or platform handlers). Pinning defends against MITM but requires a rotation plan when certs change.

var handler = new HttpClientHandler
{
    ServerCertificateCustomValidationCallback = (m, cert, chain, e) =>
        cert!.GetCertHashString() == PinnedThumbprint
};