CVE-2018-13433 in Boostnote
Summary
by MITRE
Boostnote v0.11.7 allows XSS during highlighting of Markdown text, as demonstrated by an onerror attribute of an IMG element.
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Analysis
by VulDB Data Team • 04/05/2023
The vulnerability CVE-2018-13433 affects Boostnote version 0.11.7 and represents a cross-site scripting flaw that occurs during markdown text highlighting operations. This issue specifically manifests when the application processes markdown content containing image elements with onerror attributes, creating a pathway for malicious script execution within the context of the user's browser. The vulnerability resides in how the application sanitizes and renders markdown content, particularly when handling embedded image tags that may contain malicious javascript code within their attributes.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the markdown rendering engine. When Boostnote processes markdown text containing image elements with onerror handlers, the application fails to properly sanitize these attributes before rendering them in the browser environment. This allows attackers to inject malicious javascript code that executes when the image fails to load, leveraging the onerror attribute as a vector for script execution. The flaw operates at the intersection of client-side rendering and input processing, where user-provided markdown content is directly transformed into executable html without adequate security measures.
From an operational perspective, this vulnerability poses significant risks to users who may encounter malicious markdown content in shared documents or collaborative environments. The impact extends beyond simple script execution to potentially enable more sophisticated attacks including session hijacking, data exfiltration, or redirection to malicious sites. Attackers could craft markdown documents containing crafted image tags with onerror handlers that execute malicious payloads when viewed by victims, making this particularly dangerous in collaborative note-taking environments where users frequently share content. The vulnerability affects any user who views markdown content containing malicious image tags, regardless of whether they are the content creators.
Security mitigations for this vulnerability should focus on implementing robust input sanitization and output encoding mechanisms within the markdown processing pipeline. The recommended approach involves using established sanitization libraries that properly handle html attributes and prevent script execution in contexts where user input is rendered as html. Organizations should also implement content security policies that restrict script execution and prevent inline javascript from being executed within the application context. Additionally, regular updates and patch management processes should be enforced to ensure that all users are running patched versions of the software. This vulnerability aligns with CWE-79 which describes cross-site scripting flaws, and may be mapped to ATT&CK technique T1203 which covers input validation and sanitization failures. The remediation strategy should include comprehensive testing of markdown rendering functionality and implementation of automated security scanning for user-provided content to prevent similar vulnerabilities from emerging in future versions.