A2A Java SDK is the official Java SDK for the Agent2Agent (A2A) Protocol. Starting in version 1.3.0.Final and prior to version 1.3.2.Final, the AndroidA2AHttpClient synchronous POST path overrides the disabled-redirect setting in AndroidA2AHttpClient.createConnection() with the PostBuilder default followRedirects value of true, leaving a residual of the earlier credential-redirect fix. JSONRPCTransport and RestTransport add interceptor-produced authentication headers and call synchronous post() without disabling redirects. AuthInterceptor permits X-API-Key, API-Key, X-Auth-Token, and X-Authentication headers; Android's repackaged OkHttp strips Authorization on cross-authority redirects but retains these nonstandard headers, disclosing a complete configured API key or token to another authority. The additional exposure applies when redirect or front-door behavior is compromised separately from the credential-handling component, or those components operate in different trust domains; a completely malicious initial origin already receives the credential on the first request. Autonomous clients require no human action, while user-invoked workflows can require interaction. Explicit followRedirects(false) prevents the redirected request. The demonstrated impact is credential disclosure, not subsequent credential use, integrity or availability impact, code execution, or host compromise. This issue is fixed in version 1.3.2.Final.

Affected: Maven: org.a2aproject.sdk:a2a-java-sdk-http-client-android

The GHSA-9rhm fix added this safe setting in AndroidA2AHttpClient.createConnection():

connection.setInstanceFollowRedirects(false);

The synchronous POST builder later overwrites it:

private boolean followRedirects = true;

public A2AHttpResponse post() throws IOException { HttpURLConnection connection = createConnection("POST", false); connection.setInstanceFollowRedirects(followRedirects); // ... }

The second assignment wins. JSONRPCTransport and RestTransport both add interceptor-produced headers and call synchronous post() without setting followRedirects(false).

On Android's repackaged OkHttp implementation, a cross-authority redirect strips Authorization but retains nonstandard request headers. AuthInterceptor permits four nonstandard authentication header names:

X-API-Key API-Key X-Auth-Token X-Authentication

I confirmed that the exact v1.3.1.Final Maven artifact forwards complete synthetic values under all four names to a second loopback authority. I also reproduced the supported AuthInterceptor to Android POST path. Explicitly calling followRedirects(false) returns the original 302 and produces no request to the collector.

All test traffic stayed on two ephemeral 127.0.0.1 listeners. All credentials were synthetic FULCRUM-SYNTHETIC-* values.

Reproduction

I have attached AndroidA2AHttpClientRedirectTest.java. Copy it to:

extras/http-client-android/src/test/java/org/a2aproject/sdk/client/http/android…