This suggests to me you have the tester and IOTD addons partially installed, in a broken state. For example, the language file might have been deleted, but the config option hooks left behind.
To continue any further I'd need to know more about your situation. Did you install these addons? How? Did you uninstall them? How? Is the lang_custom/EN/tester.ini file missing, but sources_custom/hooks/systems/config/bug_report_text.php there, for example?
(Click to enlarge)
#2870 - Language string missing for two security settings.
To continue any further I'd need to know more about your situation. Did you install these addons? How? Did you uninstall them? How? Is the lang_custom/EN/tester.ini file missing, but sources_custom/hooks/systems/config/bug_report_text.php there, for example?