NodeBB Forum Software is powered by Node.js and supports either Redis, MongoDB, or a PostgreSQL database. Due to an unnecessarily strict conditional in the code handling the first step of the SSO process, the pre-existing logic that added (and later checked) a nonce was inadvertently rendered opt-in instead of opt-out. This re-exposed a vulnerability in that a specially crafted Man-in-the-Middle (MITM) attack could theoretically take over another user account during the single sign-on process. The issue has been fully patched in version 1.17.2.