There seems to be a major problem in terms of screen size (resolution) fingerprinting possibility - checked on https://panopticlick.eff.org: E.g., plain Firefox 33.1.1 on WinXP SP3 Home 32 bit is shown as 1024x600x24, independently of whether the menu bar is shown or not. On the other hand, torbrowser-install-4.0.1_en-US.exe on the same machine causes following instead: - With menu bar shown (default): 1024x476x24 ("one in 1183729.75 browsers have this value") - With menu bar disabled: 1024x499x24 ("one in 175367.48 browsers have this value") As far as I remember, pre-4.0 versions of TBB had some hard-coded commonly used value, such as 1024x768x24 or something. **Trac**: **Username**: sleurn