Source: https://freeciv.fandom.com/wiki/NEWS-2.6.2.1

WHAT'S CHANGED SINCE 2.6.2 […]
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WHAT'S CHANGED SINCE 2.6.2

2.6.2.1 fixes critical build failures and crash bugs, and brings documentation updates.
Server / General
Changes affecting custom rulesets / modders Edit
Fixed server crash when unit with zero move_rate is transformed HRM#868905
Fixed crashes when using Direction objects in lua scripts HRM#880869

Clients

Fixed crash when chatline text had opening tag without closing tag HRM#887581
Fixes to the Qt client:
Fixed general memory corruption problems. It's not known what user visible symptoms these had, if any. HRM#859139
Fixed crash under certain conditions when entering the game HRM#863839
Fixed occasional crash around turn change HRM#857974 HRM#858251
Fixed crash when global observer looks at players dialog HRM#863815
Fixed memory corruption when worker task was cleared. One known symptom of this was that opening some city dialogs would crash. HRM#887748
Fixed crash when trying to use trade planning. This was reggression in 2.6.2. HRM#874406

Help / Documentation

Point to freeciv-dev mailing list as the bug reporting address. This is likely to change again in a future release. HRM#894573
Clarified that civ2civ3 ruleset Ecclesiastical Palace does not function exactly as second capital HRM#872573
Miscellaneous other improvements to in-game text and user documentation HRM#870391
Miscellaneous changes to developer/install/ruleset docs HRM#868505 HRM#857353 HRM#855637 HRM#869737 HRM#874123 HRM#880508 HRM#881455

Translations

Updated translations:
Complete translations: Spanish, French, Polish, Russian
Incomplete translations: Catalan (99% core, 100% nations, 100% ruledit), Finnish (100% core, 91% nations, 100% ruledit), Simplified Chinese (37% core, 8% nations, 3% ruledit)

Build/portability

Fixed Qt-client build against Qt-5.15 HRM#868060
Fixed problems in compiling with clang-10 HRM#868533
Fixed compiling of included lua with gcc-10 HRM#889511

Downloads: http://www.freeciv.org/download.html