CVE-2017-9244 in Trello
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Trello app before 4.0.8 for iOS might allow remote attackers to inject arbitrary web script or HTML by uploading and attaching a crafted photo to a Card.
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Analysis
by VulDB Data Team • 11/03/2019
The vulnerability identified as CVE-2017-9244 represents a critical cross-site scripting flaw within the Trello mobile application for iOS versions prior to 4.0.8. This security weakness stems from insufficient input validation and sanitization mechanisms when processing user-uploaded content, specifically photographic attachments that can be added to cards within Trello boards. The flaw creates an exploitable entry point where malicious actors can craft specially formatted image files designed to execute arbitrary JavaScript code when viewed by other users within the same Trello environment.
The technical implementation of this vulnerability resides in the application's failure to properly sanitize file metadata and content during the upload and rendering processes. When users attach photographs to cards, the iOS application does not adequately filter or escape special characters and script tags that may be embedded within image file headers or metadata. This oversight allows attackers to create malicious image files containing embedded javascript payloads that execute in the context of other users' browsers when they view the attached images. The vulnerability operates under CWE-79 which specifically addresses Cross-Site Scripting flaws, where insufficient validation of user-provided data leads to unauthorized code execution within the victim's browser context.
The operational impact of this vulnerability extends beyond simple script injection, as it enables attackers to potentially steal session cookies, perform unauthorized actions on behalf of victims, or redirect users to malicious websites. Since Trello is widely used for collaborative work environments, the attack surface is extensive with potential targets including corporate teams, project management groups, and personal users who may have access to sensitive information. The remote nature of the attack means that exploitation does not require physical access to the target device, making it particularly dangerous in enterprise settings where multiple users interact with shared boards.
Security professionals should note that this vulnerability aligns with ATT&CK technique T1566 which covers "Phishing with Malicious Attachments" and demonstrates how seemingly benign file uploads can become weaponized vectors for malicious activity. The exploitation process typically involves creating a specially crafted image file that includes malicious javascript within its metadata or embedded content, which then executes when the image is rendered in a web browser context. Organizations should implement immediate mitigations including updating to Trello version 4.0.8 or later, implementing network-level filtering for suspicious file types, and educating users about the risks of opening untrusted attachments. Additionally, organizations may consider implementing Content Security Policy headers and regular security scanning of uploaded content to prevent exploitation of similar vulnerabilities in other applications.