GHSA-8m3c-c648-2xjj

### Summary Nodemailer's `disableFileAccess` / `disableUrlAccess` options are a security sandbox that lets an application forbid untrusted message content (`html`/`text`/attachment `path`/`href`) from reading local files or making outbound HTTP(S) requests. The fix for GHSA-wqvq-jvpq-h66f (commit `5f69497`) threaded these flags through the library's internal resolution paths (`MailMessage.resolveAll()` and `_convertDataImages()`), but the public plugin API `MailMessage.resolveContent(...args)` (`lib/mailer/mail-message.js:41-43`) remains a raw passthrough to `shared.resolveContent()`. When called with the documented legacy signature `mail.resolveContent(data, key, callback)`, `shared.resolveContent` normalizes the missing options argument to an empty object (`options = options || {}`, `lib/shared/index.js:530`). The message-level flags that the `MailMessage` constructor already copied into `mail.data` (`lib/mailer/mail-message.js:34-38`) are silently discarded, so `resolveContentValue` skips both access-control guards and reaches `nmfetch(url)` (SSRF, `lib/shared/index.js:588`) or `fs.createReadStream(path)` (arbitrary file read, `lib/shared/index.js:597`). A plugin or application code that resolves message content through the documented API (the same API the library's own `_convertDataImages` uses, threading the flags explicitly) thereby bypasses the sandbox an application deliberately enabled. ### Details Root cause. The `MailMessage` constructor stores the transporter-level sandbox flags on the message object (`lib/mailer/mail-message.js:34-38`): ```js ['disableFileAccess', 'disableUrlAccess', 'normalizeHeaderKey', 'maxRecipients'].forEach(key => { if (key in options) { this.data[key] = options[key]; } }); ``` The public resolver is a pure passthrough (`lib/mailer/mail-message.js:41-43`): ```js resolveContent(...args) { return shared.resolveContent(...args); } ``` `shared.resolveContent` supports the legacy 3-argument signature and co