I am trying to upgrade Joomla from 2.5.17 to 3.5.1 from administrator panel.
In the options of "Joomla Update" I have selected "Short term support" and this is the error message that I get:
"Could not open https://update.joomla.org/core/sts/extension_sts.xml"
How can i do for this issue and update my joomla?