Critical · published April 23, 2026
A critical XSS vulnerability affected hackage-server and
hackage.haskell.org. HTML and JavaScript files provided in source
packages or via the documentation upload facility were served
as-is on the main hackage.haskell.org domain. As a consequence,
when a user with latent HTTP credentials browses to the package
pages or documentation uploaded by a malicious package maintainer,
their session can be hijacked to upload packages or
documentation, amend maintainers or other package metadata, or
perform any other action the user is authorised to do.