Discourse is an open source discussion platform. In versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0, permalinks pointing to access-restricted resources (private topics, categories, posts, or hidden tags) were redirecting users to URLs containing the resource slug, even when the user didnt have access to view the resource. This leaked potentially sensitive information (e.g., private topic titles) via the redirect Location header and the 404 pages search box. This issue is patched in versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0. No known workarounds are available.
Weakness
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Discourse | Discourse | * | 3.5.4 (excluding) |
| Discourse | Discourse | 2025.11.0 (including) | 2025.11.2 (excluding) |
| Discourse | Discourse | 2025.12.0 (including) | 2025.12.0 (including) |
| Discourse | Discourse | 2026.1.0 (including) | 2026.1.0 (including) |
Extended Description
There are many different kinds of mistakes that introduce information exposures. The severity of the error can range widely, depending on the context in which the product operates, the type of sensitive information that is revealed, and the benefits it may provide to an attacker. Some kinds of sensitive information include:
Information might be sensitive to different parties, each of which may have their own expectations for whether the information should be protected. These parties include:
Information exposures can occur in different ways:
It is common practice to describe any loss of confidentiality as an “information exposure,” but this can lead to overuse of CWE-200 in CWE mapping. From the CWE perspective, loss of confidentiality is a technical impact that can arise from dozens of different weaknesses, such as insecure file permissions or out-of-bounds read. CWE-200 and its lower-level descendants are intended to cover the mistakes that occur in behaviors that explicitly manage, store, transfer, or cleanse sensitive information.
Potential Mitigations
- Compartmentalize the system to have “safe” areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
- Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/116.html
- https://cwe.mitre.org/data/definitions/13.html
- https://cwe.mitre.org/data/definitions/169.html
- https://cwe.mitre.org/data/definitions/22.html
- https://cwe.mitre.org/data/definitions/224.html
- https://cwe.mitre.org/data/definitions/285.html
- https://cwe.mitre.org/data/definitions/287.html
- https://cwe.mitre.org/data/definitions/290.html
- https://cwe.mitre.org/data/definitions/291.html
- https://cwe.mitre.org/data/definitions/292.html
- https://cwe.mitre.org/data/definitions/293.html
- https://cwe.mitre.org/data/definitions/294.html
- https://cwe.mitre.org/data/definitions/295.html
- https://cwe.mitre.org/data/definitions/296.html
- https://cwe.mitre.org/data/definitions/297.html
- https://cwe.mitre.org/data/definitions/298.html
- https://cwe.mitre.org/data/definitions/299.html
- https://cwe.mitre.org/data/definitions/300.html
- https://cwe.mitre.org/data/definitions/301.html
- https://cwe.mitre.org/data/definitions/302.html
- https://cwe.mitre.org/data/definitions/303.html
- https://cwe.mitre.org/data/definitions/304.html
- https://cwe.mitre.org/data/definitions/305.html
- https://cwe.mitre.org/data/definitions/306.html
- https://cwe.mitre.org/data/definitions/307.html
- https://cwe.mitre.org/data/definitions/308.html
- https://cwe.mitre.org/data/definitions/309.html
- https://cwe.mitre.org/data/definitions/310.html
- https://cwe.mitre.org/data/definitions/312.html
- https://cwe.mitre.org/data/definitions/313.html
- https://cwe.mitre.org/data/definitions/317.html
- https://cwe.mitre.org/data/definitions/318.html
- https://cwe.mitre.org/data/definitions/319.html
- https://cwe.mitre.org/data/definitions/320.html
- https://cwe.mitre.org/data/definitions/321.html
- https://cwe.mitre.org/data/definitions/322.html
- https://cwe.mitre.org/data/definitions/323.html
- https://cwe.mitre.org/data/definitions/324.html
- https://cwe.mitre.org/data/definitions/325.html
- https://cwe.mitre.org/data/definitions/326.html
- https://cwe.mitre.org/data/definitions/327.html
- https://cwe.mitre.org/data/definitions/328.html
- https://cwe.mitre.org/data/definitions/329.html
- https://cwe.mitre.org/data/definitions/330.html
- https://cwe.mitre.org/data/definitions/472.html
- https://cwe.mitre.org/data/definitions/497.html
- https://cwe.mitre.org/data/definitions/508.html
- https://cwe.mitre.org/data/definitions/573.html
- https://cwe.mitre.org/data/definitions/574.html
- https://cwe.mitre.org/data/definitions/575.html
- https://cwe.mitre.org/data/definitions/576.html
- https://cwe.mitre.org/data/definitions/577.html
- https://cwe.mitre.org/data/definitions/59.html
- https://cwe.mitre.org/data/definitions/60.html
- https://cwe.mitre.org/data/definitions/616.html
- https://cwe.mitre.org/data/definitions/643.html
- https://cwe.mitre.org/data/definitions/646.html
- https://cwe.mitre.org/data/definitions/651.html
- https://cwe.mitre.org/data/definitions/79.html