Filtre does not collect any of your data. The only data the app stores are your filters and your settings. These are only saved on your device, and optionally in your own personal iCloud account. No one other than you has access to this data.
Because of the way Filtre works, the Filtre extension needs to have permission to access every website you visit. This is needed because Filtre has to analyze the contents of a website, to determine what should be filtered, and apply those filters. Filtre does not store any information about the websites you're visiting. Not even locally on your device.
If you report an issue with a website through the app, that report is sent to a server, and stored in a database that only I, the developer of the app, can access. The only information that is stored is: the (sub)domain of the website, the full URL of the page if you optionally included it, the version of the app, the kind of device that you were using (iPhone/iPad/Mac), and an anonymized hash of your IP address.
If you have any additional questions or remarks, feel free to reach out to me! You can reach me at jeffrey@filtre.app.