Hello Demis,
We sincerely apologize for the inconvenience caused.
This issue has been fixed in SP Page Builder v6.6.2. Once you upgrade to v6.6.2, this specific vulnerability can no longer be exploited.
However, if your site was compromised before upgrading, simply updating the extension will not remove any malicious files or backdoors that may have already been uploaded. If those files remain on the server, attackers may still be able to access your site. Therefore, it is important to perform a complete cleanup before considering the site secure.
Please follow the cleanup guide here: https://www.joomshaper.com/forum/question/45152
You can also use the following security scanner to help identify malicious files and delete them: https://github.com/zkrana/joomla-security-scanner
Please make sure to read the README.md file in the repository for instructions on how to run the tool.
After completing the cleanup and upgrading to v6.6.2, please let us know the outcome or if you need any further assistance. We'll be happy to help.
Thank you.