update SECURITY.md

SECURITY.md

@@ -2,20 +2,21 @@
 
 ## Supported Versions
 
-Use this section to tell people about which versions of your project are
-currently being supported with security updates.
-
 | Version | Supported          |
 | ------- | ------------------ |
-| 5.1.x   | :white_check_mark: |
-| 5.0.x   | :x:                |
-| 4.0.x   | :white_check_mark: |
-| < 4.0   | :x:                |
+| 4.4.x   | :white_check_mark: |
+| < 4.3   | :x:                |
+
+## Reporting Security Issues
+
+If you believe you have found a security vulnerability in any GROWI related repository, **please do not report security vulnerabilities through public GitHub issues.**
+
+Instead, please report it to us using one of the methods described below.
 
-## Reporting a Vulnerability
+  * [Join our Slack team](https://growi-slackin.weseek.co.jp/) and send DM to `@yuki` who is the lead developer
+  * Report to JPCERT/CC ([en](https://www.jpcert.or.jp/english/ir/form.html)/[ja](https://www.jpcert.or.jp/form/))
 
-Use this section to tell people how to report a vulnerability.
+## Preferred Languages
 
-Tell them where to go, how often they can expect to get an update on a
-reported vulnerability, what to expect if the vulnerability is accepted or
-declined, etc.
+Communication in English and Japanese is possible.  
+In Japanese, we can reply more quickly.