A2A Java SDK send client credentials under server-controlled HTTP header name, enabling leakage via redirect
Impact.* A malicious or compromised A2A agent can cause the client's API key credential to be forwarded to an arbitrary third-party server. The agent serves an AgentCard with an APIKeySecurityScheme specifying a custom header name, then responds with an HTTP redirect. The JDK HttpClient follows the redirect and forwards the custom header containing the credential, since only the standard Authorization header may be stripped on cross-origin redirects.