As you can see by consulting the following page in Security Headers:
I recommend inserting the following lines in the .htaccess file of the next ClipBucket’s version:
Header set X-XSS-Protection "1; mode=block"
Header set X-Content-Type-Options nosniff
Header set Strict-Transport-Security "max-age=63072000; includeSubDomains: preload"
Header always append X-Frame-Options SAMEORIGIN
The above lines are documented and have been tested. For the remaining vulnerabilities, it may be useful to consult the free tool offered by Mozilla: https://observatory.mozilla.org/
Good use of ClipBucket in safety