nette/nette — pull request #642 by OndrejSlamecka (2012-05-06 00:39:31+00:00)
Title: Config/Configurator: Improved detectDebugMode

Servers running Varnish cache with default settings are mistakenly detected as a local environment and therefore debug mode is enabled.
Varnish passes HTTP header HTTP_X_FORWARDED_FOR and this could be used to detect Varnish installation. (see https://www.varnish-cache.org/docs/3.0/faq/http.html or default.vcl in Varnish files)
Only possible threat I can see is falling into safer non-debug state.