From e3564e2e7e6638f550f22b57df8c357b5c1265d4 Mon Sep 17 00:00:00 2001
From: Piotr Wegrzynek <pwe@trifork.com>
Date: Fri, 5 Jun 2026 12:47:24 +0200
Subject: [PATCH] Perform XPath lookups on private XML node copy to maintain
 thread safety

---
 .../CoreDataStorage/XMPPMessageArchivingCoreDataStorage.m    | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Extensions/XEP-0136/CoreDataStorage/XMPPMessageArchivingCoreDataStorage.m b/Extensions/XEP-0136/CoreDataStorage/XMPPMessageArchivingCoreDataStorage.m
index de644e946..a53114927 100644
--- a/Extensions/XEP-0136/CoreDataStorage/XMPPMessageArchivingCoreDataStorage.m
+++ b/Extensions/XEP-0136/CoreDataStorage/XMPPMessageArchivingCoreDataStorage.m
@@ -208,9 +208,12 @@ - (XMPPMessageArchiving_Message_CoreDataObject *)composingMessageWithJid:(XMPPJI
 
 - (BOOL)messageContainsRelevantContent:(XMPPMessage *)message
 {
+    // The underlying XML processing is thread safe for read access only: https://github.com/robbiehanson/KissXML/wiki/MemoryManagementThreadSafety
+    // XPath-based node lookup has to be performed on a copy as it requires temporary document assignment and therefore is not a strictly read operation
+    XMPPMessage *messageCopy = [message copy];
     for (NSString *XPath in self.relevantContentXPaths) {
         NSError *error;
-        NSArray *nodes = [message nodesForXPath:XPath error:&error];
+        NSArray *nodes = [messageCopy nodesForXPath:XPath error:&error];
         if (!nodes) {
             XMPPLogError(@"%@: %@ - Error querying XPath (%@): %@", THIS_FILE, THIS_METHOD, XPath, error);
             continue;