As the version number implies, Pale Moon x64 15.4 is based on the Gecko 15 engine used in Firefox 15, with the developer openly making no attempt to keep up with Mozilla’s six-week development cycle in favour of polishing and securing the older browser engine.
Version 15.4 adds no new features, but includes a number of security updates and bug fixes that make Pale Moon as secure as the latest version of Firefox, currently at 18.0.
Pale Moon 15.4 comes with eight specific fixes: the first two deal with security concerns raised in two separate Mozilla Foundation Security Advisories, namely MSFA 2013-20, dealing with bogus Turktrust certificates, and MSFA 2013-01, which fixes several memory security hazards. Both have also been plugged in the latest versions of Firefox.
Version 15.4 also aims to fix potential font-related exploits by updating the OTS library to r95, and also includes a security fix for the libpixman stack buffer overflow.
There are also non-security improvements, notably a fix for certain types of input lag on sites with unnecessary DOM invalidations, which include Twitter and Facebook. There’s improved pipelining logic through a fix for HTTP pipelining re-use, and both performance and stability improvements to cario and direct2d back-end. Performance has also been improved for repeat gradients.
Pale Moon 15.4 is based on Firefox 15’s functionality, but unlike Firefox also ships as a dedicated Windows 64-bit build for improved performance. With the Waterfox project currently stuck at version 16.0.1 along with Mozilla’s own decision to abandon a 64-bit Windows build, Pale Moon remains one of the best options for 64-bit Windows users.
and Pale Moon x64 15.4 are both available as freeware downloads for PCs running Windows XP SP3 or later, as are portable builds Pale Moon 15.4 Portable and Pale Moon x64 15.4 Portable.