[Racket announcement] Racket v6.9

Racket version 6.9 is now available from

    http://racket-lang.org/

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Security Announcement:

A security vulnerability in the `racket/sandbox` library and Typed
Racket allowed malicious Typed Racket code to escape the sandbox.
This vulnerability has been fixed in Racket version 6.9. Anyone using
`racket/sandbox` to execute untrustworthy code with access to Typed
Racket should upgrade to version 6.9 immediately.

While this known vulnerability has been eliminated, it is possible that
similar errors in other installed collections could also be exploited,
although we are not currently aware of any existing vulnerabilities. We
recommend that if you use the Racket sandbox to execute untrustworthy
Racket code, you should also employ additional operating system or
virtual machine level protections. The documentation for `racket/sandbox`
has been updated to list recommended security practices for using the
library.

Thanks to Scott Moore for identifying this vulnerability.

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- The official package catalog Web site is revised to have a new user
  experience.

- The Northwestern snapshot site keeps weekly snapshots going up to 12
  weeks into the past. Those provide a middle ground for users who want
  access to new features earlier than stable releases, but want less
  churn than nightly builds.

- DrRacket provides a refactoring tool to remove unused requires in
  modules.

- DrRacket's #lang-line customization support works better with buggy
  (i.e., in development) languages.

- The web server's cookie libraries, including "id cookie" authentication,
  support RFC 6265.

- The `db` library supports PostgreSQL's UUID type.

- The `raco` command lists matching commands when passed an ambiguous
  command prefix.

- The bytecode compiler detects more optimization opportunities for
  structure operations.

- Scribble can produce output via XeLaTeX as an alternative to LaTeX.

- Scribble supports the `acmart` LaTeX style, for use with ACM
  publications.

- Scribble supports the use of CJK characters in tags.

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The following people contributed to this release:
Alex Knauth, Alexander Shopov, Alexis King, Andrew Kent, Asumu Takikawa,
Ben Greenman, Daniel Feltey, David Van Horn, Georges Dupéron, Greg
Hendershott, Gustavo Massaccesi, Ingo Blechschmidt, James Bornholt,
James Whang, Jay McCarthy, Jeff Shelley, John Clements, Jordan Johnson,
Leandro Facchinetti, Leif Andersen, Marc Burns, Matthew Butterick,
Matthew Eric Bassett, Matthew Flatt, Matthias Felleisen, Michael Myers,
Mike Sperber, Philip McGrath, Philippe Meunier, Robby Findler, Royall
Spence, Ryan Culpepper, Sam Caldwell, Sam Tobin-Hochstadt, Shu-Hung You,
Spencer Florence, Stephen Chang, Tony Garnock-Jones, Vincent St-Amour,
WarGrey Gyoudmon Ju, Wei Tang, and William G Hatch.

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