CVE-2007-1970 in Firefox
Summary
by MITRE
Mozilla Firefox does not warn the user about HTTP elements on an HTTPS page when the HTTP elements are dynamically created by a delayed document.write, which allows remote attackers to supply unauthenticated content and conduct phishing attacks.
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Analysis
by VulDB Data Team • 10/15/2017
This vulnerability exists in Mozilla Firefox versions prior to 2.0.0.2 and represents a critical security flaw related to mixed content handling and user interface warnings. The issue specifically manifests when HTTP resources are dynamically loaded onto HTTPS pages through delayed document.write operations, creating a scenario where users remain unaware of the insecure content being rendered. The vulnerability stems from Firefox's failure to properly detect and warn users about mixed content that is injected after the initial page load, particularly when this injection occurs through JavaScript delayed execution mechanisms.
The technical implementation of this flaw involves the browser's security model not properly tracking dynamically inserted HTTP elements within HTTPS contexts. When a webpage loads over HTTPS but subsequently uses document.write to inject HTTP resources such as images, scripts, or iframes after the initial page rendering, Firefox fails to recognize this as mixed content and does not display the expected security warning. This behavior creates a significant attack surface for malicious actors who can exploit the gap in security warnings to inject unauthorized content that appears to be part of the legitimate secure page.
The operational impact of this vulnerability is severe and directly enables sophisticated phishing attacks. Attackers can leverage this flaw to create convincing deceptive interfaces that appear secure to users while actually loading malicious content from unencrypted sources. The delayed nature of the document.write execution makes detection particularly challenging as the security warning system cannot anticipate or properly flag content that is injected after the initial page load. This vulnerability specifically enables credential theft, malware distribution, and other malicious activities that rely on user trust in the secure connection indicator.
The security implications extend beyond simple phishing attacks to encompass broader trust model violations within web browsers. This vulnerability aligns with CWE-614, which addresses sensitive data exposure through insecure communication channels, and represents a failure in the browser's mixed content blocking mechanisms. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access through deceptive user interfaces and social engineering attacks that exploit browser trust models. The flaw essentially undermines the fundamental security principle that HTTPS connections should provide consistent protection throughout the entire page lifecycle.
Mitigation strategies for this vulnerability include immediate browser updates to versions that properly implement mixed content detection for dynamically loaded elements. Users should ensure their Firefox installations are updated to version 2.0.0.2 or later, which includes enhanced detection mechanisms for delayed document.write operations. Organizations should implement comprehensive security awareness training to help users recognize potential phishing attempts, particularly those involving seemingly legitimate secure pages with unexpected insecure content. Additionally, web developers should avoid using delayed document.write operations for injecting HTTP resources and instead implement proper HTTPS resource loading to prevent exploitation of this vulnerability. The fix implemented by Mozilla involved enhancing the browser's mixed content detection system to properly track and warn users about dynamically injected HTTP elements regardless of when they are loaded into the page context.