If you want to use this module, your options are:
- Choose another, actively maintained module instead
- File an issue in the queue with a patch to fix the module and then contact the security team to have your version reviewed and the project handed over to you following the unsupported project process.
- Hire someone to fix the security bug so the module can be re-published (see this guide on how to hire a Drupal site developer)
SexyBookmarks is no longer being actively maintained. It was a port of Shareaholic for WordPress, and Shareaholic has since released an official Drupal module.
Recommended next step:
You can learn more here: https://blog.shareaholic.com/drupal-module/