Fix redacted events being returned in search results ordered by "recent"

changelog.d/6522.bugfix

@@ -0,0 +1 @@
+Prevent redacted events from being returned during message search.

synapse/storage/data_stores/main/search.py

@@ -385,7 +385,7 @@ def search_msgs(self, room_ids, search_term, keys):
         """
         clauses = []
 
-        search_query = search_query = _parse_query(self.database_engine, search_term)
+        search_query = _parse_query(self.database_engine, search_term)
 
         args = []
 
@@ -501,7 +501,7 @@ def search_rooms(self, room_ids, search_term, keys, limit, pagination_token=None
         """
         clauses = []
 
-        search_query = search_query = _parse_query(self.database_engine, search_term)
+        search_query = _parse_query(self.database_engine, search_term)
 
         args = []
 
@@ -606,7 +606,12 @@ def search_rooms(self, room_ids, search_term, keys, limit, pagination_token=None
 
         results = list(filter(lambda row: row["room_id"] in room_ids, results))
 
-        events = yield self.get_events_as_list([r["event_id"] for r in results])
+        # We set redact_behaviour to BLOCK here to prevent redacted events being returned in
+        # search results (which is a data leak)
+        events = yield self.get_events_as_list(
+            [r["event_id"] for r in results],
+            redact_behaviour=EventRedactBehaviour.BLOCK,
+        )
 
         event_map = {ev.event_id: ev for ev in events}