Create SECURITY.md (#1238)

* Create SECURITY.md

* Correct typo

* review fixes

* add sentence

README.md

@@ -2,9 +2,16 @@
 
 > Authenticator generates 2-Step Verification codes in your browser.
 
-## Available for Chrome, Firefox, Microsoft Edge and Safari
+## Available for Chrome, Firefox, and Microsoft Edge
 
-[<img src="https://raw.githubusercontent.com/wiki/Authenticator-Extension/Authenticator/readme-images/chrome-web-store.png" title="Chrome Web Store" width="170" height="48" />](https://chrome.google.com/webstore/detail/authenticator/bhghoamapcdpbohphigoooaddinpkbai) [<img src="https://raw.githubusercontent.com/wiki/Authenticator-Extension/Authenticator/readme-images/firefox-add-ons.png" title="Firefox Add-ons" width="170" height="48" />](https://addons.mozilla.org/en-US/firefox/addon/auth-helper?src=external-github) [<img src="https://raw.githubusercontent.com/wiki/Authenticator-Extension/Authenticator/readme-images/microsoft-store.png" title="Microsoft Store" height="48">](https://microsoftedge.microsoft.com/addons/detail/ocglkepbibnalbgmbachknglpdipeoio) [<img width="150" alt="Download on the App Store" src="https://developer.apple.com/assets/elements/badges/download-on-the-app-store.svg"/>](https://apps.apple.com/us/app/authen/id1602945200?mt=12)
+[<img src="https://raw.githubusercontent.com/wiki/Authenticator-Extension/Authenticator/readme-images/chrome-web-store.png" title="Chrome Web Store" width="170" height="48" />](https://chrome.google.com/webstore/detail/authenticator/bhghoamapcdpbohphigoooaddinpkbai) [<img src="https://raw.githubusercontent.com/wiki/Authenticator-Extension/Authenticator/readme-images/firefox-add-ons.png" title="Firefox Add-ons" width="170" height="48" />](https://addons.mozilla.org/en-US/firefox/addon/auth-helper?src=external-github) [<img src="https://raw.githubusercontent.com/wiki/Authenticator-Extension/Authenticator/readme-images/microsoft-store.png" title="Microsoft Store" height="48">](https://microsoftedge.microsoft.com/addons/detail/ocglkepbibnalbgmbachknglpdipeoio) 
+
+
+### Safari Edition
+
+A Safari edition of Authenticator is available on the App Store. We do not provide official support for the Safari edition.
+
+[<img width="150" alt="Download on the App Store" src="https://developer.apple.com/assets/elements/badges/download-on-the-app-store.svg"/>](https://apps.apple.com/us/app/authen/id1602945200?mt=12)
 
 ## Build Setup
 

SECURITY.md

@@ -0,0 +1,11 @@
+# Security Policy
+
+## Supported Versions
+
+We support the latest versions published on the Chrome, Firefox, and Edge extension stores.
+
+## Reporting a Vulnerability
+
+Report potential vulnerabilities privately via [this form](https://github.com/Authenticator-Extension/Authenticator/security/advisories/new).
+Where appropriate, include a proof-of-concept and reproduction steps.
+We strive to provide an initial response within five days, but as this is a volunteer-run project, we make no guarantees.