A stored cross-site scripting (XSS) vulnerability exists in ZZCMS2023 in the ask/show.php file at line 21. An attacker can exploit this vulnerability by sending a specially crafted POST request to /user/ask_edit.php?action=add, which includes malicious JavaScript code in the 'content' parameter. When a user visits the ask/show_{newsid}.html page, the injected script is executed in the context of the user's browser, leading to potential theft of cookies, session tokens, or other sensitive information.