I would be more concerned about the site building software that you are using. If you provide the name perhaps we could look for known vulnerabilities.
If the site you are building either stores user input (in a database for instance) insecurly and then displays it again it could be vulnerable to XSS.
Also if it reflects user input that could also be used for XSS. By reflect I mean it takes some user input and insecurely renders it to the screen immediately without storing it on the server side. On example would be if the following URL:
Thanks for confirming your account with the email: email@example.com!
Depending on what the script you are embedding does, there could be some risk but you're probably okay.
XSS flaws generally appear in scenarios where your page pulls in untrusted content from a 3rd party. That can be GET or POST arguments, data from a database, HTTP headers, etc.
If the answer to both of those questions is no, then you're probably good to go.