GHSA-cr3w-cw5w-h3fj: Saltcorn's Reflected XSS and Command Injection vulnerabilities can be chained for 1-click-RCE

1. There is a reflected XSS vulnerability in the GET /admin/edit-codepage/:name route through the name parameter. This can be used to hijack the session of an admin if they click a specially crafted link.
2. Additionally, there is a Command Injection vulnerability in GET /admin/backup. The admin can inject a shell command in the backup password which is inserted in the command used to create the backup zip.

Both vulnerabilities can be chained to craft a malicious link which will execute an arbitrary shell command on the server if it is clicked by a saltcorn admin with an active session. I believe iframes could also be used to exploit this silently when the admin visits an attacker-controlled web page (though I have not tested that).