We fixed the main issue of this form in CVE-2020-9444, but the audit
done at that time only included links found in rendered_markdown; this
change completes our audit for links with target=_blank anywhere in
the codebase.
This fixes a bundle of issues where we were missing "" around
attributes coming from variables. In most cases, the variables were
integers or fixed constants from the Zulip codebase (E.g. the name of
an installed integration), but in at least one case it was
user-provided data that could potentially have security impact.
While we could fix this issue by changing the markdown processor,
doing so is not a robust solution, because even a momentary bug in the
markdown processor could allow cached messages that do not follow our
security policy.
This change ensures that even if our markdown processor has bugs that
result in rendered content that does not properly follow our policy of
using rel="noopener noreferrer" on links, we'll still do something
reasonable.
Co-authored-by: Tim Abbott <tabbott@zulipchat.com>
Signed-off-by: Anders Kaseorg <anders@zulipchat.com>
Tim Abbott
Anders Kaseorg
vinitS101