CVE-2017-7815 in Firefox
Summary
by MITRE
On pages containing an iframe, the "data:" protocol can be used to create a modal dialog through Javascript that will have an arbitrary domains as the dialog's location, spoofing of the origin of the modal dialog from the user view. Note: This attack only affects installations with e10 multiprocess turned off. Installations with e10s turned on do not support the modal dialog functionality. This vulnerability affects Firefox < 56.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 01/15/2021
This vulnerability represents a sophisticated cross-origin spoofing attack that exploits a specific quirk in Firefox's handling of modal dialogs within iframe contexts. The security flaw arises from the improper validation of the data protocol when creating modal dialog interfaces, allowing attackers to manipulate the perceived origin of these dialogs through JavaScript manipulation. The vulnerability specifically targets installations where the e10s (Electrolysis) multiprocess architecture is disabled, which represents a significant subset of older Firefox configurations where the security model is less robust. The attack vector leverages the ability to construct modal dialogs using the data: protocol, which creates a unique opportunity for origin spoofing that directly impacts user trust and security expectations. This represents a classic case of trust boundary violation where the browser's security model fails to properly validate the source of dialog origins.
The technical implementation of this vulnerability exploits the difference in security handling between Firefox installations with and without e10s enabled. When e10s is disabled, the browser maintains a less secure single-process model where iframe content can more easily manipulate dialog origins through JavaScript execution. The flaw occurs because the browser does not properly validate that the origin of a modal dialog matches the actual source of the content, allowing malicious actors to present false origins in dialog interfaces. This particular vulnerability demonstrates the complexity of modern browser security models where disabling certain security features can create unexpected attack surfaces. The data: protocol, typically used for embedding small amounts of data directly in URLs, becomes a vector for creating deceptive user interfaces that can mislead users about the true source of security warnings or prompts.
The operational impact of this vulnerability extends beyond simple spoofing, as it can enable more sophisticated social engineering attacks where users might be tricked into trusting malicious dialog origins. Users interacting with compromised web pages could be misled into believing they are seeing legitimate security warnings or prompts from trusted domains, when in fact these interfaces are being generated from arbitrary origins. This creates a dangerous trust model disruption where user security decisions could be based on false information presented through the modal dialog interface. The vulnerability affects Firefox versions prior to 56, representing a significant window of potentially vulnerable installations where users were exposed to this spoofing risk without adequate protection mechanisms. This type of attack directly undermines the browser's security model and user confidence in the authenticity of security interfaces.
The mitigation strategy for this vulnerability requires either upgrading to Firefox version 56 or later, which includes fixes for the e10s multiprocess architecture handling, or ensuring that e10s is enabled in Firefox configurations. Organizations should prioritize updating their Firefox installations to eliminate this attack surface entirely, as the vulnerability only affects legacy configurations. The fix implemented in Firefox 56 addresses the underlying security model issue by properly validating dialog origins and ensuring that modal interfaces cannot be spoofed through the data: protocol mechanism. This vulnerability aligns with CWE-601 and ATT&CK techniques related to URL redirection and user interface deception, demonstrating how seemingly minor implementation flaws can create significant security risks in browser environments. Security teams should monitor for this vulnerability in legacy systems and ensure proper patch management protocols are in place to protect against similar spoofing attacks that may target other browser components or security interfaces.