如果他们有权访问修改。下面的链接描述了xss和css（跨站脚本）。他们可以重定向您的背景作为一个示例

http：// www.acunetix.com/websitesecurity/cross-site-scripting/

It can if they have access to modify. The below link describes xss and css (cross site scripting). They can redirect your background as one example http://www.acunetix.com/websitesecurity/cross-site-scripting/