Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, the hasAccessToLabel function contains a SQL operator precedence bug that allows any authenticated user to read any label that has at least one task association, regardless of project access. Label titles, descriptions, colors, and creator information are exposed. This vulnerability is fixed in 2.3.0.

Affected: Go: code.vikunja.io/api

## Summary

The `hasAccessToLabel` function contains a SQL operator precedence bug that allows any authenticated user to read any label that has at least one task association, regardless of project access. Label titles, descriptions, colors, and creator information are exposed.

## Details

The access control query at `pkg/models/label_permissions.go:85-91` uses xorm's query chain in a way that produces SQL without proper grouping:

```go has, err = s.Table("labels"). Select("label_tasks.*"). Join("LEFT", "label_tasks", "label_tasks.label_id = labels.id"). Where("label_tasks.label_id is not null OR labels.created_by_id = ?", createdByID). Or(cond). And("labels.id = ?", l.ID). Exist(ll) ```

The xorm chain `.Where(A OR B).Or(C).And(D)` generates SQL: `WHERE A OR B OR C AND D`. Because SQL AND has higher precedence than OR, this evaluates as `WHERE A OR B OR (C AND D)`. The `labels.id = ?` constraint (D) only binds to the project access condition (C), while `label_tasks.label_id IS NOT NULL` (part of A) remains unconstrained.

Any label that has at least one task association passes the `IS NOT NULL` check, regardless of who is requesting it.

## Proof of Concept

Tested on Vikunja v2.2.2.

```python import requests

TARGET = "http://localhost:3456" API = f"{TARGET}/api/v1"

def login(u, p): return requests.post(f"{API}/login", json={"username": u, "password": p}).json()["token"]

def h(token): return {"Authorization": f"Bearer {token}", "Content…