html/template: disallow angle brackets in CSS values
Angle brackets should not appear in CSS contexts, as they may affect
token boundaries (such as closing a <style> tag, resulting in
injection). Instead emit filterFailsafe, matching the behavior for other
dangerous characters.
Thanks to Juho Nurminen of Mattermost for reporting this issue.
Fixes #59720
Fixes CVE-2023-24539
Change-Id: Iccc659c9a18415992b0c05c178792228e3a7bae4
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/
1826636
Reviewed-by: Julie Qiu <julieqiu@google.com>
Run-TryBot: Roland Shoemaker <bracewell@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/491615
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>