Other controversial decisions include the browser only being released for Microsoft Windows and featuring both the Gecko rendering engine of previous releases and the Trident engine used in Internet Explorer, and switching between them based on a "compatibility list" that came with the browser. This effectively exposed users to the security vulnerabilities in both and resulted in a completely different user experience based on which site they were on. Examples are handling of right-to-left or bi-directional text, user interface widgets, bugs and web standards violations in Trident, etc. On top of this, Netscape Browser 8 even broke Internet Explorer's ability to open XML files by damaging a Windows Registry key, and would do so every time it was opened, even if the user fixed it manually.