CVE-2016-4618 in iOS
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Safari Reader in Apple iOS before 10 and Safari before 10 allows remote attackers to inject arbitrary web script or HTML via a crafted web site, aka "Universal XSS (UXSS)."
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability identified as CVE-2016-4618 represents a critical cross-site scripting flaw in Apple Safari's Reader functionality affecting iOS versions prior to 10 and Safari versions before 10. This universal XSS vulnerability specifically targets the Reader component that processes and displays web content, creating a persistent security risk that enables attackers to execute malicious scripts within the context of a user's browsing session. The flaw operates at a fundamental level where user input is not properly sanitized during the content rendering process, allowing attackers to craft malicious web pages that can execute arbitrary code when processed by Safari's Reader module.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within Safari's Reader component, which processes web content for display in a simplified reading view. When users navigate to malicious websites that exploit this vulnerability, the Reader module fails to properly escape or filter user-supplied content, creating an XSS vector that can be leveraged across different web contexts. This particular flaw is classified under CWE-79 as Improper Neutralization of Input During Web Page Generation, specifically manifesting as a cross-site scripting vulnerability in web applications. The Universal XSS designation indicates that the vulnerability can be exploited across multiple domains and contexts, amplifying its potential impact beyond typical XSS scenarios where exploitation is often limited to a single domain.
The operational impact of CVE-2016-4618 extends beyond simple script execution, as it enables attackers to perform session hijacking, steal sensitive user data, manipulate web content, and potentially gain unauthorized access to user accounts. The vulnerability affects millions of iOS users who relied on Safari's Reader feature for content consumption, creating a significant attack surface that could be exploited for large-scale data breaches or malicious activity. Attackers could craft phishing pages that appear legitimate to users while simultaneously executing malicious scripts that harvest cookies, credentials, or other sensitive information from the user's browsing session. This vulnerability directly aligns with ATT&CK technique T1059.006 for Command and Scripting Interpreter: JavaScript and T1566.001 for Phishing: Spearphishing Attachment, as it enables both script execution and social engineering attacks that can bypass traditional security controls.
Mitigation strategies for this vulnerability required immediate system updates and patches from Apple, as the flaw existed in the core browser functionality that users could not easily disable or modify. Organizations should have implemented network-level protections such as web application firewalls and content filtering solutions to detect and block malicious payloads attempting to exploit this vulnerability. Users were advised to upgrade to iOS 10 and Safari 10 releases that contained the necessary security patches, while also implementing browser security enhancements such as content security policies and strict sanitization of web content. The vulnerability highlights the importance of proper input validation and output encoding in web applications, particularly in components that process user-generated content or external data sources. Security professionals should have monitored for exploitation attempts and implemented comprehensive security awareness training to help users recognize potential phishing attempts that could leverage this vulnerability. The incident underscored the critical need for regular security updates and the importance of maintaining current browser versions to protect against known vulnerabilities that could be exploited for unauthorized access to user data and system resources.