You can import categories in bulk, by giving the CSV file, on admin side you need to select the category in which you want to import and then just browse the csv file to upload.
We are not aware of any vulnerabilities for this plugin. This does not mean that the plugin is secure, nor does it mean that it is insecure.
Is this your plugin?
We offer WordPress plugin security testing to help identify security vulnerabilities within your plugin. Please note that this is a paid service. If you are interested in talking about having your plugin tested by WordPress security experts, get in touch.