This repository contains a XSS vulnerable (simple) guestbook application (src-vuln). A fixed version is provided as well (src-fixed). This example requires a SQL database and a webserver to run. It was created as an exercise for a security course at university.
┌────────────────────────┐
│ Guestbook page │
│ (index.php) │
└────────────────────────┘
▲
│
Fetch data and display it
│
┌─────────────────────────┐
│ MySQL Database │
└─────────────────────────┘
▲
│
Insert data w/o sanitizing input (Fixed
version: w/ sanitizing input)
│
┌─────────────────────────┐
│ Add Comment page │
│ (jumbotron-add.php) │──┐
└─────────────────────────┘ │
▲ │
│ │
└───────────────┘
Submit Form via Post
Page prints inserted comment, if
an error occured.
Created with Monodraw
The vulnerable version of the application tries to store the user input directly into the database. (Stored XSS, as the guestbook page simply prints the values take from the database.) In case the database is not able to store the data, an error is returned and the submitted message is printed. (Reflected XSS, as input leading to an error message will be printed as well and could contain executable code.)
In the fixed version of this application htmlentities( SubmittedValue, ENT_QUOTES ) is used to convert special characters into their html representation. (http://php.net/manual/de/function.htmlentities.php)
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