test: wire leaky.eml into the anti-leak suite (red, defect 2)

test_no_ioc_holds_a_recipient_address grepped for the literal
"example.org", and every existing fixture hides the recipient address
as base64, so URL redaction could be disabled entirely and both this
test and test_cli's counterpart stayed green.

leaky.eml carries you@example.org in five URL shapes plus a From
display-name trap. Adding it to the fixture list, plus a new test
asserting on the raw address and its percent-encoded form, turns the
suite red: the valueless-query-parameter defect (redact.py) currently
lets ?victim@example.org through as a kept parameter NAME. Left
failing on purpose; the next commit fixes redact.py and turns it
green.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KphFXTc2QajxXsHWyvGJ4R

2 files changed, 29 insertions, 1 deletions

diff --git a/tests/fixtures/leaky.eml b/tests/fixtures/leaky.eml
new file mode 100644
index 0000000..840ce6d
--- /dev/null
+++ b/tests/fixtures/leaky.eml
@@ -0,0 +1,20 @@
+Received: from mx.example.org (mx.example.org [192.0.2.11])
+	by mail.example.org (Postfix) with ESMTP id III99
+	for <you@example.org>; Tue, 8 Sep 2026 16:00:02 +0200 (CEST)
+Received: from sender.example.invalid (unknown [203.0.113.42])
+	by mx.example.org (Postfix) with ESMTP id JJJ11
+	for <you@example.org>; Tue, 8 Sep 2026 16:00:01 +0200 (CEST)
+Return-Path: <bounce@sender.example.invalid>
+From: "Billing at billing@innocent.example" <phish@sender.example.invalid>
+To: <you@example.org>
+Subject: Confirm now
+Message-ID: <eee555@sender.example.invalid>
+Date: Tue, 8 Sep 2026 16:00:00 +0200
+MIME-Version: 1.0
+Content-Type: text/plain; charset=utf-8
+
+Plain value:      http://a.example.invalid/p?e=you@example.org
+Valueless param:  http://b.example.invalid/p?you@example.org
+In the fragment:  http://c.example.invalid/p#e=you@example.org
+In userinfo:      http://you%40example.org:pw@d.example.invalid/p
+Nested redirect:  http://t.example.invalid/c?url=http%3A%2F%2Fe.example.invalid%2Fp%3Fe%3Dyou%40example.org
diff --git a/tests/test_parse.py b/tests/test_parse.py
index 28c8609..a29b7a1 100644
--- a/tests/test_parse.py
+++ b/tests/test_parse.py
@@ -213,12 +213,20 @@ class TestIocAssembly(unittest.TestCase):
     def test_no_ioc_holds_a_recipient_address(self):
         # The safety property, asserted over the whole output.
         for name in ("simple.eml", "forged-chain.eml", "with-attachment.eml",
-                     "redirector.eml"):
+                     "redirector.eml", "leaky.eml"):
             iocs = parse.iocs(load(name), trusted=["192.0.2.0/24"])
             blob = repr(iocs)
             self.assertNotIn("you@example.org", blob)
             self.assertNotIn("example.org", blob)
 
+    def test_the_address_does_not_survive_any_url_shape(self):
+        # leaky.eml carries you@example.org in five placements. Each one has
+        # been a real leak in this codebase or is one shape away from it.
+        iocs = parse.iocs(load("leaky.eml"), trusted=["192.0.2.0/24"])
+        blob = repr(iocs)
+        self.assertNotIn("you@example.org", blob)
+        self.assertNotIn("you%40example.org", blob)
+
 
 if __name__ == "__main__":
     unittest.main()