Here's some release notes:
2016-05-12 - Snort 2.9.9 Beta
[*] New additions
* HTTP/2 support.
HTTP2 SUPPORT IS STILL EXPERIMENTAL.
By default, HTTP2 traffic is not supported. To enable it you need:
* Install nghttp library from https://nghttp2.org/
* If nghttp is not installed in default path, use with_libnghttp2_includes and
with_libnghttp2_libraries to point to the correct path during "configure" step.
* Enable HTTP2 support in http_inspect configuration with "legacy_mode no"
Refer README.http_inspect for details.
* Buffer Dump feature.
Enable buffer dump feature with "--enable-buffer-dump" configure option.
* Rule options - byte_math, bitmask and from_end.
[*] Improvements
* Performance improvements to AppID.
* Fixed Flash LZMA decompression issue.
* Added 802.11/wifi header support in ARP Preprocessor.
* Stability improvement for Stream6 preprocessor.
* Fixed multiple issues in HttpInspect preprocessor.
* Fixed an issue of incorrect masking of sensitive data.
Check out Snort 2.9.9, available for download on our site.