Version 3.5, codenamed Shiretoko, adds a variety of new features to Firefox. Initially numbered Firefox 3.1, Mozilla developers decided to change the numbering of the release to 3.5, in order to reflect a significantly greater scope of changes than originally planned.These changes include support for the and tags as defined in the HTML 5 specification, with a goal to offer video playback without being encumbered by patent issues associated with many video technologies.Cross-site XMLHttpRequests (XHR), which can allow for more powerful web applications and an easier way to implement mashups, are also implemented in 3.5. A new global JSON object contains native functions to efficiently and safely serialize and deserialize JSON objects, as specified by the ECMAScript 3.1 draft. Full CSS 3 selector support has been added. Firefox 3.5 uses the Gecko 1.9.1 engine, which includes a few features that were not included in the 3.0 release. Multi-touch support was also added to the release, including gesture support like pinching for zooming and swiping for back and forward. Firefox 3.5 also features an updated logo. The first update, 3.5.1, was released on July 16, 2009, which solved some vulnerabilities detected after the initial release. And the second update, 3.5.2, was released on July 29, 2009.