Version 2.6-10 is now on CRAN. See NEWS for user-visible changes. These are not many. The main reason for the release was that 2.6-8 had "undefined behaviour" in one C function. This change was not mentioned in NEWS, because I could not be sure that the issue was fixed. I was personally pretty confident of fixing this but I could not replicate the CRAN test results nor guarantee that they were fixed. Current CRAN tests are OK so presumably the issue was fixed. Although undefined behaviour is undefined the issue seems to be harmless because function did not access the item when it was undefined. The issue is very technical: if you really are interested, the critical bug fix is 525dce5.
Full Changelog: v2.6-8...v2.6-10