Remote code execution is possible through server-side template injection (SSTI), a flaw where an application improperly handles template inputs, allowing an attacker to inject and execute malicious code on the server. This issue specifically affects XLSX templates because the `xltpl` library utilizes a non-sandboxed Jinja environment for template processing. Successful exploitation allows user-supplied code to run within the server context as the document-merge-server user (UID 901), granting significant control over the container.