CVE-2024-22075 is a medium severity vulnerability identified in Firefly III, an open-source personal finance manager application, affecting versions prior to 6.1.1. The vulnerability is classified as an HTML Injection issue occurring through the application's webhook functionality. Specifically, this vulnerability allows an attacker to inject malicious HTML content into webhook payloads or parameters, which can then be rendered in the user's browser context. The underlying weakness corresponds to CWE-79, indicating Cross-Site Scripting (XSS) or HTML Injection flaws. The CVSS 3.1 base score is 6.1, reflecting a network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), but requiring user interaction (UI:R). The scope is changed (S:C), meaning the vulnerability can affect components beyond the initially vulnerable component. The impact on confidentiality and integrity is low (C:L, I:L), with no impact on availability (A:N). This suggests that an attacker could potentially execute malicious scripts in the context of a victim's browser session, leading to limited data disclosure or manipulation within the application, but not causing denial of service or full system compromise. No known exploits are currently reported in the wild, and no official patches or vendor advisories are linked yet. The vulnerability is significant because Firefly III is used by individuals and organizations to manage sensitive financial data, and exploitation could lead to theft of session tokens, unauthorized actions, or phishing attacks leveraging the trusted application interface. The requirement for user interaction implies that an attacker must trick a user into triggering the malicious webhook or viewing crafted content. The changed scope indicates that the impact could extend beyond the immediate component, potentially affecting other parts of the application or user sessions.

For European organizations using Firefly III, this vulnerability poses a risk to the confidentiality and integrity of financial data managed within the application. Although the impact is rated medium, the sensitivity of financial information means that even limited data leakage or manipulation can have serious consequences, including financial fraud or unauthorized transactions. The requirement for user interaction reduces the risk of automated widespread exploitation but increases the risk of targeted attacks such as spear phishing or social engineering campaigns. Organizations that integrate Firefly III with other financial systems or expose webhook endpoints publicly may face increased exposure. Additionally, compromised user sessions could lead to lateral movement within organizational networks if credentials or tokens are stolen. The vulnerability could undermine trust in financial management processes and lead to regulatory compliance issues under GDPR if personal data is exposed. Given the growing adoption of open-source financial tools in Europe, the threat could affect both private individuals and small to medium enterprises relying on Firefly III for budgeting and accounting.

To mitigate CVE-2024-22075, organizations should promptly upgrade Firefly III to version 6.1.1 or later once the patch is available. In the interim, administrators should restrict webhook usage to trusted sources and validate or sanitize all webhook inputs rigorously to prevent injection of malicious HTML content. Implement Content Security Policy (CSP) headers to limit the execution of injected scripts in browsers. Educate users about the risks of interacting with unsolicited webhook notifications or links. Monitor webhook endpoints for unusual or suspicious payloads. Employ web application firewalls (WAFs) with rules targeting XSS and HTML injection patterns. Review and harden authentication and session management mechanisms to reduce the impact of potential session hijacking. Conduct regular security assessments and code reviews focusing on input validation and output encoding in webhook-related components. Finally, maintain an incident response plan to quickly address any exploitation attempts.