The vulnerability identified as CVE-2026-16391 involves information disclosure within the IndexedDB storage component of Mozilla Firefox. IndexedDB is a web storage technology used by web applications to store significant amounts of structured data. The flaw could allow an attacker to gain access to sensitive information stored in IndexedDB. Mozilla fixed this vulnerability in Firefox 153 and Firefox ESR 140.13 as part of a broader security update addressing multiple high and moderate impact issues. The vendor advisory confirms the fix and provides multiple bug references for tracking.

Successful exploitation of this vulnerability could lead to unauthorized disclosure of information stored in the IndexedDB component, potentially exposing sensitive user data. However, there are no reports of active exploitation in the wild. The impact is rated as moderate by Mozilla.

Mozilla has released official fixes for this vulnerability in Firefox 153 and Firefox ESR 140.13. Users and administrators should update affected Firefox installations to these versions or later to remediate the issue. Since the vulnerability is fixed in these versions, no additional mitigation steps are required beyond applying the official update.