myBB Forums 1.8.26 Stored Cross-Site Scripting via Template Management

Advisories

severity: medium
date: December 22, 2025
Affecting: myBB forums 1.8.26
CVE: CVE-2023-53976
CWE: CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVSS: 5.1
CVSS V4 Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
References: ExploitDB-51136
Official myBB Software Version Page
Credit: Andrey Stoykov
Description: myBB Forums 1.8.26 contains a stored cross-site scripting vulnerability in the template management system that allows authenticated administrators to inject malicious scripts when creating new templates. Attackers can exploit this vulnerability by inserting script payloads in the template title field when adding new templates through the 'Templates and Style' > 'Templates' > 'Manage Templates' > 'Global Templates' interface, causing arbitrary JavaScript to execute when the template is viewed.