Usage of native GUI controls for web content rendering allows fingerprinting
TBB is using native OS GUI controls in Web content (scrollbars, check boxes, comba boxes, ...).
If a user has customized the OS UI settings (e.g. scrollbar size) or installed a custom OS theme, a web page can detect the different control metrics.
This applies at least on Windows. On Linux, TBB appears to ignore the GTK OS config.