Update SECURITY.md

SECURITY.md

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 If you believe you have found a security vulnerability in any GROWI related repository, please report it to us using one of the methods described below.
 
   * [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/))
+  * Report to JPCERT/CC[^jpcertcc]
+    * [[PDF] JPCERT/CC Vulnerability Coordination and Disclosure Policy](https://www.jpcert.or.jp/english/vh/vul-coordination-disclosure-policy_2019.pdf)
 
 ## Preferred Languages
 
 Communication in English and Japanese is possible.  
 In Japanese, we can reply more quickly. 
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+Some long sentence. 
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+[^jpcertcc]: JPCERT/CC is a National CSIRT in Japan and a coordination center
+who coordinates cyber security incidents and products vulnerabilities
+with network service providers, product vendors (software/IoT/ICS etc.),
+security vendors, government agencies, as well as the industry associations.