doc: simplify valid security issue descriptions

PR-URL: #23881
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

README.md

@@ -182,18 +182,17 @@ nonetheless.
### Private disclosure preferred

- [CVE-2016-7099](https://nodejs.org/en/blog/vulnerability/september-2016-security-releases/):
  _Fix invalid wildcard certificate validation check_. This is a high severity
  defect that would allow a malicious TLS server to serve an invalid wildcard
  certificate for its hostname and be improperly validated by a Node.js client.
  _Fix invalid wildcard certificate validation check_. This was a high-severity
  defect. It caused Node.js TLS clients to accept invalid wildcard certificates.

- [#5507](https://github.com/nodejs/node/pull/5507): _Fix a defect that makes
  the CacheBleed Attack possible_. Many, though not all, OpenSSL vulnerabilities
  in the TLS/SSL protocols also affect Node.js.

- [CVE-2016-2216](https://nodejs.org/en/blog/vulnerability/february-2016-security-releases/):
  _Fix defects in HTTP header parsing for requests and responses that can allow
  response splitting_. While the impact of this vulnerability is application and
  network dependent, it is remotely exploitable in the HTTP protocol.
  response splitting_. This was a remotely-exploitable defect in the Node.js
  HTTP implementation.

When in doubt, please do send us a report.