Chamilo LMS is an open-source learning management system. From 2.0.0 through at least 2.1.0, Chamilo LMS stores private Message.content without server-side sanitization and renders it as HTML in assets/vue/views/message/MessageShow.vue and public/main/template/default/message/view_message.html.twig. An authenticated low-privilege user, including a student, can directly address crafted message content to an administrator because the message creation flow permits a sender to select another user as the recipient. The content executes in the recipient's browser when the recipient opens the routine inbox or message view, without requiring a link click, and can expose session credentials or permit actions as the administrator. This vulnerability is fixed in 2.0.1.