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Attack Surface Analysis for daneden/animate.css

Attack Surface: CSS Injection Vulnerabilities

  • Description: Exploiting vulnerabilities where an attacker can inject malicious CSS code into the application, potentially leading to Cross-Site Scripting (XSS) or phishing attacks, by manipulating how animate.css classes are applied.
  • How animate.css contributes to the attack surface: If your application dynamically constructs CSS class names or styles based on user-controlled input and directly uses these to apply animate.css classes, it creates a direct pathway for CSS injection. The animate.css library provides the CSS classes that become the vehicle for the injected malicious styles when class names are built insecurely.
  • Example: An application feature allows users to preview animated text. The application takes user input for the animation effect and naively constructs a class string like "animate__animated animate__" + userInput. If a malicious user inputs "shakeX; /* style="x:expression(javascript:alert('XSS'))" */" , the resulting class attribute could become class="animate__animated animate__shakeX; /* style="x:expression(javascript:alert('XSS'))" */". In older browsers that support CSS expressions, this could lead to XSS execution. Even without CSS expressions, injected CSS can be used to overlay malicious content or alter the page in harmful ways for phishing.
  • Impact:
    • Cross-Site Scripting (XSS): In certain browser contexts or when combined with other vulnerabilities, CSS injection can be leveraged for XSS attacks.
    • Phishing Attacks: Malicious CSS can be used to visually manipulate the page to mimic login forms or trusted elements, leading to credential theft.
    • Account Takeover (Indirect): If phishing is successful, it can lead to account compromise.
    • Data Theft (Indirect): Injected CSS, combined with other vulnerabilities, could potentially be used to exfiltrate sensitive data.
  • Risk Severity: High (Can escalate to Critical in scenarios leading to XSS or successful phishing)
  • Mitigation Strategies:
    • Eliminate Dynamic CSS Generation from User Input: The most critical mitigation is to completely avoid constructing CSS class names or styles dynamically based on any user-provided input.
    • Use Predefined Allowlist of animate.css Classes: Implement a strict allowlist of permitted animate.css class names. Only allow selection from this predefined, safe list.
    • Content Security Policy (CSP): Enforce a strong CSP that restricts style-src and unsafe-inline directives to minimize the impact of any potential CSS injection.
    • Regular Security Audits and Code Reviews: Conduct regular security audits and code reviews to identify and remediate any instances of insecure CSS handling, especially where animate.css classes are involved.
    • Framework/Library Security Features: Utilize security features provided by your development framework or libraries to prevent or mitigate CSS injection vulnerabilities.

By prioritizing these mitigations, especially eliminating dynamic CSS generation from user input and using a predefined allowlist, developers can effectively address the high-severity CSS injection risk directly related to using animate.css in potentially vulnerable ways.