The browser is based on Firefox ESR and this release brings it up-to-date with Firefox 45-ESR, providing better support for HTML5 video on YouTube.
The browser can be run from removable media and is available for Windows, Mac OS X, and GNU/Linux.
The 6.0 series introduces code-signing for OS X systems in order to help users who had difficulty getting the browser to work on the Mac due to Gatekeeper interference.
The new release has privacy enhancements and disables features for which the team did not have the time to write a proper fix or where they decided it was potentially harmful in the context of privacy.
This release also ensures that SHA1 certificate support is disabled and the updater is not relying on the signature alone but checks the hash of a downloaded update file as well before applying it. There is also a fix for a Windows installer-related DLL hijacking vulnerability.
The team said it was now using DuckDuckGo as its default search engine, through its meta search provider, Disconnect. Google was used earlier but Disconnect now has no access to Google anymore.
There is some history to this: Disconnect was banned from Android in 2014 and it then filed an anti-trust complaint against Google with European regulators, accusing the search company of abusive conduct.