CVE-2026-77143 in TYPO3
Summary
by MITRE • 08/25/2026
The frontend topic editing flow does not verify on the server side that the requesting visitor owns the topic being modified. As a result, a visitor who knows the identifier of a topic from the public forum can submit a modified update request for that topic directly and overwrite its content, without the application confirming ownership. Topic identifiers are visible in the public forum listing, and exploitation requires no privileged access or non-default configuration.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 08/25/2026
The vulnerability described constitutes a critical Insecure Direct Object Reference (IDOR) flaw within the frontend topic editing workflow of the affected web application. This security defect arises from a fundamental failure to implement proper server-side authorization checks when processing requests intended to modify existing forum topics. Specifically, the backend logic relies exclusively on the client-supplied identifier for the target resource without validating whether the authenticated user initiating the request holds legitimate ownership or administrative privileges over that specific topic. In secure application design, every state-changing operation must verify not only authentication but also authorization by ensuring the current session's identity is linked to the requested resource through a robust access control mechanism. The absence of this verification allows any actor with knowledge of the target identifier to bypass intended restrictions and execute unauthorized modifications.
Topic identifiers are typically exposed in public forum listings, search results, or URL structures, making them easily discoverable by external attackers without requiring any form of privileged access or exploitation of non-default configurations. This visibility significantly lowers the barrier for entry, enabling a wide range of actors from script kiddies to sophisticated threat groups to target specific content with precision. The operational impact of this vulnerability is severe, as it allows an attacker to overwrite legitimate user-generated content, inject malicious payloads such as cross-site scripting (XSS) vectors or phishing links into forum posts, deface the application's public-facing information, and potentially disrupt community trust by spreading misinformation. Furthermore, if the topic editing functionality interacts with other system components, this flaw could serve as a pivot point for more complex attacks, including data exfiltration or further privilege escalation depending on how the modified content is processed downstream.
From a classification perspective, this vulnerability aligns directly with CWE-284, which describes Improper Access Control where an actor gains access to resources they are not authorized to use. It also maps closely to OWASP Top 10 categories related to Broken Access Control and Insecure Direct Object References. The exploitation technique mirrors the ATT&CK tactic of Initial Access or Impact via Content Injection, specifically leveraging the ability to manipulate application state through unvalidated inputs. To mitigate this issue, developers must implement strict server-side authorization checks for all editing endpoints. This involves retrieving the topic record from the database and verifying that the user ID associated with the active session matches the owner_id field of the target resource before allowing any write operations. Additionally, implementing role-based access control (RBAC) can ensure that only users with specific permissions such as author or moderator can edit content. Input validation should also be reinforced to sanitize data entering the system, preventing secondary injection attacks through the modified fields. Regular security audits and penetration testing focused on horizontal privilege escalation scenarios are recommended to identify similar gaps in other parts of the application logic.