The vulnerability stems from missing X-Frame-Options or Content-Security-Policy headers in admin page responses, which would typically be controlled by framework-level security configurations or middleware rather than specific userland functions. However, without access to EC-CUBE's source code, commit diffs, or patch details, we cannot definitively identify the exact functions/file paths responsible for rendering admin pages or setting security headers. The vulnerability is architectural (missing security headers) rather than tied to a specific business logic function. This analysis is based on: 1) The CWE-1021 pattern of missing frame protection headers 2) EC-CUBE being a Symfony-based PHP application where headers would typically be set in controllers or middleware 3) The advisory's description matching clickjacking via unprotected admin interfaces.