Note 1: The list of major changes is described on Piwigo 2.0.0 release notes. This page only describes what changes between release 2.0.9 and release 2.0.10.
Note 2: release 2.0.10 is not release 2.1.0. (you will have to wait another week for it)

Languages

• Srpski (Serbian) was added, thanks to Darko
• 0001526: [configuration] add links to ru.piwigo.org
• 0001527: [configuration] add links to hu.piwigo.org

Features Added

• 0001119: [category management] ability to sort categories in reverse order
• 0000986: [search] [admin maintenance screen] ability to clear *_search table

Bugs Fixed

• 0001523: [configuration] Compatibility with PHP 5.3, missing iso.txt file
• 0001621: [security] XSS vulnerability in register.php, reported by VUPEN Security vupen.com
• 0001486: [language] missing localization

Upgrade

To upgrade a Piwigo 2.0.x installation, you can follow 2 methods:

• The automatic way: use the Piwigo Auto Upgrade plugin as described in forum topic Piwigo Auto Upgrade for the impatient.
• The manual way: download the 2.0.x_to_2.0.10.zip archive that contains all new or modified files. Once you have extracted files, transfer them on your web server with a FTP client (like FileZilla) over your Piwigo 2.0.x installation. No database upgrade is required.

To upgrade a Piwigo installation older than 2.0.0, read the upgrade guide.