OpenClaw versions prior to 2026.4.2 have a vulnerability in the Zalo webhook replay deduplication mechanism where dedupe keys are not sufficiently scoped across chat and sender dimensions. This can cause legitimate webhook events from different conversations or senders to be incorrectly identified as duplicates and dropped. The issue leads to silent message suppression and disrupts bot workflows, impacting availability of webhook event processing. A fix is available in version 2026.4.2.