Task titles, project titles, team names, doer/assignee names, and API
token titles were interpolated raw into Line(...) calls whose content is
rendered to HTML by goldmark and then sanitized with bluemonday UGCPolicy.
UGCPolicy intentionally allows safe <a href> and <img src> with
http/https URLs, so a title containing Markdown link or image syntax
would survive sanitization as a working phishing link or tracking pixel
in a legitimate Vikunja email.
Introduce notifications.EscapeMarkdown, which prefixes every CommonMark
§2.4 backslash-escapable ASCII punctuation character — including '<' so
autolinks like `<https://evil.com>` are neutralized before reaching
goldmark — with a backslash. Apply it to every user-controlled argument
of every Line(...) call in pkg/models that feeds into an i18n template,
and to the hand-built "* [title](url) (project)" Markdown link in the
overdue-tasks digest notification.
Also escape the migration error string in MigrationFailedNotification,
an additional sink not listed in the advisory (error messages can carry
user-controlled content from the external migration source).
Subject(...), Greeting(...), and CreateConversationalHeader(...) are
left unchanged: Subject is passed directly to the mail library and is
not markdown-rendered, Greeting is rendered via html/template's built-in
HTML escaping without markdown, and the conversational header is
sanitized as raw HTML by bluemonday in mail_render.go.
Fixes GHSA-45q4-x4r9-8fqj.
0f3730d045