[20180507] Session deletion race condition

A long running background process, such as remote checks for core or extension updates, had created a race condition where a session which was expected to be destroyed would be recreated.

This vulnerability affects the following application versions:

• Joomla 3.5.0



• Joomla 3.5.0-rc



• Joomla 3.5.0-rc2



• Joomla 3.5.0-rc3



• Joomla 3.5.0-rc4



• Joomla 3.5.1



• Joomla 3.5.1-rc



• Joomla 3.5.1-rc2



• Joomla 3.6.0



• Joomla 3.6.0-rc



• Joomla 3.6.0-rc2



• Joomla 3.6.1



• Joomla 3.6.1-rc1



• Joomla 3.6.1-rc2



• Joomla 3.6.2



• Joomla 3.6.3



• Joomla 3.6.3-rc1



• Joomla 3.6.3-rc2



• Joomla 3.6.3-rc3



• Joomla 3.6.4



• Joomla 3.6.5



• Joomla 3.7.0



• Joomla 3.7.0-rc1



• Joomla 3.7.0-rc2



• Joomla 3.7.0-rc3



• Joomla 3.7.0-rc4



• Joomla 3.7.1



• Joomla 3.7.1-rc1



• Joomla 3.7.1-rc2



• Joomla 3.7.2



• Joomla 3.7.3



• Joomla 3.7.3-rc1



• Joomla 3.7.3-rc2



• Joomla 3.7.4



• Joomla 3.7.4-rc1



• Joomla 3.7.5



• Joomla 3.8.0



• Joomla 3.8.0-rc1



• Joomla 3.8.1



• Joomla 3.8.1-rc



• Joomla 3.8.2



• Joomla 3.8.2-rc



• Joomla 3.8.3



• Joomla 3.8.3-rc



• Joomla 3.8.4



• Joomla 3.8.4-rc



• Joomla 3.8.4-rc2



• Joomla 3.8.5



• Joomla 3.8.5-rc



• Joomla 3.8.6



• Joomla 3.8.6-rc1



• Joomla 3.8.7



• Joomla 3.8.7-rc



• Joomla 3.8.8-rc