Looking for logging into the Joomla 2.5 28 Update Invalid site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Joomla 2.5 28 Update Invalid site. After that you can login as usual with your login credentials.
https://forum.joomla.org/viewtopic.php?t=868651
http://www.joomlaportal.de/joomla-2-5-allgemeine-fragen/304115-bei-update-error-invalid-login.html
https://joomla.stackexchange.com/questions/8984/update-joomla-from-2-5-28-to-3-4-0
https://github.com/joomla/joomla-cms/issues/17514
https://forum.joomla.de/thread/2047-update-von-joomla-2-5-28-auf-3-5-1-endet-mit-einer-fehlermeldung/
https://stackoverflow.com/q/28963158
https://joomlanl.nl/forum/63-2-5-x-installatie-upgrade-backup-en-verhuizing/41076-error-invalid-login-joomla-2-511-to-2-513
https://www.joomshaper.com/blog/upgrade-from-joomla-2-5-to-joomla-3-x-is-not-so-scary
https://www.joomla-tips.org/joomla-troubleshooter/error-invalid-login-during-joomla-upgrade.html
https://joomla-tips.net/joomla-install-config/joomla-troubleshooter/
https://www.kunena.org/forum/k-3-0-installation-and-upgrade/132418-failed-upgrade-to-kunena-3-0-7
https://joomlaforum.ru/index.php/topic,283896.0.html
https://www.joomlashack.com/blog/joomla/how-to-upgrade-from-joomla-2-5-to-joomla-3/