Description of my issue:
Hi Nicolas,
In the last Akeeba Backup Pro version 3.11.1 there is a bug with the plugin: 'System - Backup on update' . When this plugin is enabled we get the 403 error when trying to update to Joomla 2.5.21 (from 2.5.20) and also when trying to update to Joomla 3.3.1 (from 3.3.0)
When I disable the plugin in Plug-in manager I can update again in both Joomla versions.
So there is something wrong with this plug-in!
Please fix.
Best regards,
Klipper