Go to app / config / core.php
In this file, find
Configure::write('Session.timeout', '120');
Session timeout (in seconds), the default is 120 seconds. You can edit it here as needed. Now the actual timeout duration depends on
Configure::write('Security.level', 'medium'); if 'high' then Session timeout in 'Session.timeout' x 10, if 'medium' then Session timeout in 'Session.timeout' x 100, if 'low' Session timeout in 'Session.timeout' x 300
Thus, by combining Session.timeout and Security.level you can get the desired session timeout
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