Note: Plugins are developed and provided by third parties. Some Sigil developers are also plugin developers but this is separate from Sigil itself. Plugins can be open source as well as proprietary. No vetting by a Sigil developer (unless a Sigil developer wrote the plugin) is performed. Use your judgment if you install and use a plugin. We cannot be held responsible for what a third party plugin that you the user actively installed and ran.
Also, realize that Plugins are separate from Sigil and have their own authors. They aren’t part of Sigil. If you have an issue with a plugin you’ll need to take that up with the person(s) who made the plugin.
Again, we at Sigil have no control over plugins and what they actually do.