Vikunja versions >= 0.24.0 and <= 2.3.0 contain a broken object level authorization (BOLA) vulnerability in the task-collection endpoint (GET /api/v1/projects/{project}/views/{view}/tasks). The endpoint loads the requested project view from the URL path without verifying the caller is authorized for it. For a link-share token holder, the task scope is pinned to the share's own project, but the view is taken from the attacker-controlled path and never re-validated. As a result, a holder of any project share link can read any other tenant's kanban bucket records — bucket titles and the full created_by user object (username, name, id) — for every view in the instance. The same missing pre-authorization view load also creates a project/view-ID existence oracle (404 vs. non-404) usable by link shares and ordinary authenticated users. Task contents remain constrained to the share's own project and are not disclosed. Fixed in 2.4.0.

Vikunja versions 0.22.0 through 2.3.0 fail to validate the principal type in API token management. Because user IDs and link-share IDs are independent numeric sequences and both resolve through a generic web.Auth.GetID() interface, a link-share JWT whose numeric ID equals a target user's ID is treated as that user by the /api/v1/tokens endpoints. An authenticated attacker can obtain a target's numeric user ID via authenticated user search, then create link shares on an attacker-writable project until the link-share sequence reaches that value, and use the resulting link-share JWT to list, create, and delete the target user's API tokens (including issuing a new token with attacker-chosen scopes under the target's permissions). Fixed in version 2.4.0.

Vikunja before 2.2.1 contains an authorization flaw where the LinkSharing.ReadAll endpoint exposes share hashes to users with read access, enabling permission escalation to admin-level shares. The GetTaskAttachment endpoint performs permission checks against user-supplied task IDs but fetches attachments by sequential ID without verifying ownership, allowing attackers to download and delete all file attachments across all projects instance-wide.

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, the CalDAV GetResource and GetResourcesByList methods fetch tasks by UID from the database without verifying that the authenticated user has access to the task's project. Any authenticated CalDAV user who knows (or guesses) a task UID can read the full task data from any project on the instance. This vulnerability is fixed in 2.3.0.

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, Vikunja's link share authentication (GetLinkShareFromClaims in pkg/models/link_sharing.go) constructs authorization objects entirely from JWT claims without any server-side database validation. When a project owner deletes a link share or downgrades its permissions, all previously issued JWTs continue to grant the original permission level for up to 72 hours (the default service.jwtttl). This vulnerability is fixed in 2.3.0.

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, the Vikunja file import endpoint uses the attacker-controlled Size field from the JSON metadata inside the import zip instead of the actual decompressed file content length for the file size enforcement check. By setting Size to 0 in the JSON while including large compressed file entries in the zip, an attacker bypasses the configured maximum file size limit. This vulnerability is fixed in 2.3.0.

Vikunja is an open-source self-hosted task management platform. Prior to version 2.2.2, the `LinkSharing.ReadAll()` method allows link share authenticated users to list all link shares for a project, including their secret hashes. While `LinkSharing.CanRead()` correctly blocks link share users from reading individual shares via `ReadOne`, the `ReadAllWeb` handler bypasses this check by never calling `CanRead()`. An attacker with a read-only link share can retrieve hashes for write or admin link shares on the same project and authenticate with them, escalating to full admin access. Version 2.2.2 patches the issue.

Vikunja is an open-source self-hosted task management platform. Prior to version 2.2.1, the `GET /api/v1/projects/:project/webhooks` endpoint returns webhook BasicAuth credentials (`basic_auth_user` and `basic_auth_password`) in plaintext to any user with read access to the project. While the existing code correctly masks the HMAC `secret` field, the BasicAuth fields added in a later migration were not given the same treatment. This allows read-only collaborators to steal credentials intended for authenticating against external webhook receivers. Version 2.2.1 patches the issue.

Vikunja is an open-source self-hosted task management platform. Starting in version 0.13 and prior to version 2.2.1, any user that has enabled 2FA can have their TOTP reused during the standard 30 second validity window. Version 2.2.1 patches the issue.

Vikunja is an open-source self-hosted task management platform. Starting in version 0.21.0 and prior to version 2.2.0, the Vikunja Desktop Electron wrapper passes URLs from `window.open()` calls directly to `shell.openExternal()` without any validation or protocol allowlisting. An attacker who can place a link with `target="_blank"` (or that otherwise triggers `window.open`) in user-generated content can cause the victim's operating system to open arbitrary URI schemes, invoking local applications, opening local files, or triggering custom protocol handlers. Version 2.2.0 patches the issue.