External web links (http/https) in rendered email bodies open in a new browser
tab with target="_blank" rel="noopener noreferrer". mailto:, tel:, and in-page
#anchors keep their default behavior instead of spawning a blank tab.
The plaintext render path is already handled on main by #594 (ADD_URI_SAFE_ATTR
in PLAIN_TEXT_RENDERED_CONFIG), so this no longer adds its own hook there — the
plaintext linkifier only ever emits http(s) anchors, so the config's declarative
exemption is sufficient. This change covers the paths #594 did not:
- iframe HTML render: both anchor passes (the DOMPurify hook and the post-render
DOM walk in email-viewer.tsx) set target=_blank on EVERY <a>, including
mailto:/tel:. Now scoped to http(s) via the shared applyNewTabToAnchor()
helper (http/https -> target+rel; mailto/tel/#/other -> strip target/rel).
- sanitizeI18nHtml: the same DOMPurify strip dropped target/rel from translated
links (e.g. the docs link in settings.security.not_available, target="_blank"
in 19/22 locales). Keep the author's target and harden rel="noopener
noreferrer".
Tests: unit coverage for isHttpLinkHref / applyNewTabToAnchor / sanitizeI18nHtml
plus an integration suite over the real plaintext and HTML/iframe render
pipelines. The plaintext-hook-specific cases are dropped as redundant with #594.
