added 'Hidden directories' tutorial

- signed-off-by: trimstray <trimstray@gmail.com>

README.md

@@ -381,6 +381,7 @@ performance of any of your sites from across the globe.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://media.defcon.org/DEF%20CON%2026/"><b>DEF CON Media Server</b></a> - great stuff from DEFCON 26.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://labs.ripe.net/Members/cteusche/bgp-meets-cat"><b>BGP Meets Cat</b></a> - after 3072 hours of manipulating BGP, Job Snijders has succeeded in drawing a Nyancat.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://robertheaton.com/2018/11/28/https-in-the-real-world/"><b>HTTPS in the real world</b></a> - great tutorial explain how HTTPS works in the real world.<br>
+&nbsp;&nbsp;:small_orange_diamond: <a href="https://medium.com/@_bl4de/hidden-directories-and-files-as-a-source-of-sensitive-information-about-web-application-84e5c534e5ad"><b>Hidden directories</b></a> - hidden directories and files as a source of sensitive information about web application.<br>
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