The 6th level of the OverTheWire Natas wargame starts introducing us to PHP and server configuration issues.
It starts out with a secret password prompt.
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I took a look at the sourcecode, via the link provided.
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I decided I would try and see if I could request the “secret.inc” file, and it worked perfectly.
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After I put in the secret value into the input box, it showed me the password for the next level.
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This level teaches that files that contain secrets should never be publicly accessible. Either put them in server-side code so that they’re not rendered, or put them out of the webroot.