Proof of concept
1. As an admin user authorized for plugins, go to the YouTube Embed Profiles page.
2. Choose a profile from the drop down list on the right and click 'Change profile'.
3. Enter an XSS payload (e.g. <script>alert(1)</script>) into the 'Profile name' field.
4. Log out and log in as a super admin or a different admin.
5. Navigate to the YouTube Embed Options page.
This has been tested with Firefox 38.2.0 on Debian.
Upgrade the plugin to version 3.3.3 or later.
2015-08-19: Requested vulnerability reporting instructions via vendor support form
2015-08-20: Vendor asked that vulnerability be reported on the vendor's website plugin page
2015-08-20: Reported to vendor via plugin page
2015-08-20: Requested CVE number
2015-08-23: Vendor released version 3.3.3 – confirmed fixed
2015-08-26: Public Disclosure