CVE-2017-7762 in Firefox
Summary
by MITRE
When entered directly, Reader Mode did not strip the username and password section of URLs displayed in the addressbar. This can be used for spoofing the domain of the current page. This vulnerability affects Firefox < 54.
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Analysis
by VulDB Data Team • 12/28/2020
This vulnerability resides in the Firefox browser's Reader Mode functionality, specifically within how it handles URL parsing and display in the address bar. The flaw represents a critical information disclosure and user interface spoofing issue that could be exploited by malicious actors to deceive users about the true origin of web content. When users navigated to web pages through Reader Mode, the browser failed to properly sanitize the URL by removing authentication credentials from the address bar display, creating a potential attack vector for phishing and social engineering campaigns. The vulnerability existed in Firefox versions prior to 54, making a substantial user base susceptible to this security weakness.
The technical implementation of this flaw stems from improper URL sanitization within Firefox's Reader Mode component. When a user accessed a web page containing authentication credentials in the URL such as https://user:[email protected], the browser would display the complete URL including the username and password portion in the address bar. This behavior allowed attackers to craft malicious URLs that could display a legitimate domain name while actually pointing to a different, potentially malicious destination. The vulnerability specifically affected the address bar rendering logic that was responsible for displaying page information to users, creating a false sense of security when users believed they were visiting a trusted domain. This issue falls under the CWE category of CWE-20: Improper Input Validation, as the system failed to properly validate and sanitize URL components before displaying them to users.
The operational impact of this vulnerability extends beyond simple spoofing, as it could enable sophisticated phishing attacks and credential theft operations. Attackers could create malicious websites that appear to display legitimate domain names in the browser address bar while actually redirecting users to phishing pages or malware distribution sites. This capability undermines the fundamental security principle of user trust in browser address bar information and could lead to unauthorized data access, credential compromise, and further exploitation. The vulnerability particularly affected users who relied on Reader Mode for content consumption, as it created a false positive environment where users might trust malicious domains that appeared legitimate in the address bar. This weakness aligns with ATT&CK technique T1566.001: Phishing: Spearphishing Attachment, where attackers could use this spoofing capability to increase the credibility of their phishing campaigns and improve user engagement rates.
Mitigation strategies for this vulnerability required immediate browser updates to Firefox version 54 or later, which implemented proper URL sanitization in Reader Mode. Users should have been advised to disable Reader Mode when visiting suspicious websites or when dealing with sensitive information. Security administrators needed to implement browser hardening policies that enforced automatic updates and monitored for vulnerable browser versions within their networks. Organizations should have considered implementing additional network-level protections such as URL filtering and content inspection systems that could detect and block malicious URLs with authentication credentials. The fix involved modifying Firefox's URL parsing and display logic to ensure that authentication components were stripped from URLs before being rendered in the address bar, regardless of the browsing mode being used. This remediation addressed the core issue by implementing proper input validation and sanitization procedures that align with security best practices for web browser development and user interface design.