Today we published our first ever maintenance release of the WiX Toolset. WiX Toolset v3.9 R2 fixes three bugs (listed below) that were deemed too serious to wait for v3.10. You do not need to upgrade to v3.9 R2 unless you hit one of these issues.
Bug 4600 | VSExtension Help custom action binaries are corrupt.
Bug 4608 | Multiple prerequisites return failure, when 1st prerequisite is already installed and 2nd prerequisite is installed successfully.
Bug 4609 | Bug in BVariantCopy() in src/burn/engine/variant.cpp