Arundir: Titan's Quest has been updated to 2.6.
Changelog from Steam:
Are you sure you did not post the wrong changelog? The actual release here on GOG (Galaxy only for now) is 2.7 and this is the changelog for said update (also taken from Steam):
Fixed several collision and nav. mesh issues
Fixed various crash bugs
Fixed playing Custom Maps, resource files can now be read correctly.
Fixed Tier 7 skill connections showing in the base game
Fixed some Atlantis uniques having a low drop chance
Fixed monster scaling when playing high level chars in Normal Tartarus
Boss and hero monster health now scale more strongly with number of players
Tartarus "No pets allowed" modifier: Pets are not forcibly removed when arena starts
Fixed incorrect duration bar display for certain buffs.
Pets that spawn from projectiles remember their behavior setting
Tweaked enemy spawns in the final area
Fixed delayed poison trap effects in Hades & Atlantis
Fixed missing properties on Hesperide MI armors
Fixed Poison Mayhem % at level 1 and progression at ultimate levels
Poison Mayhem fear duration changed to 1-2s
Added 0.7s cooldown to Lightning Dash (window for passive procs)
Added chance to freeze and do extra damage to Lightning Dash
Increased range of Sylvan Nymph arrows
Quest "A score to settle" is now assigned to Atlantis region. (It may disappear from the journal if already listed.)
Changed format of all enemy sounds to fix functions such as distance falloff
Several graphical fixes
Various minor tweaks and fixes