Merge pull request #170010 from MicrosoftDocs/repo_sync_working_branch

Confirm merge from repo_sync_working_branch to master to sync with https://github.com/MicrosoftDocs/azure-docs (branch master)

Author: huypub

articles/active-directory/develop/scenario-spa-overview.md

@@ -32,7 +32,7 @@ Many modern web applications are built as client-side single-page applications.
 
 The Microsoft identity platform provides **two** options to enable single-page applications to sign in users and get tokens to access back-end services or web APIs:
 
-- [OAuth 2.0 Authorization code flow (with PKCE)](./v2-oauth2-auth-code-flow.md). The authorization code flow allows the application to exchange an authorization code for **ID** tokens to represent the authenticated user and **Access** tokens needed to call protected APIs. In addition, it returns **Refresh** tokens that provide long-term access to resources on behalf of users without requiring interaction with those users. This is the **recommended** approach.
+- [OAuth 2.0 Authorization code flow (with PKCE)](./v2-oauth2-auth-code-flow.md). The authorization code flow allows the application to exchange an authorization code for **ID** tokens to represent the authenticated user and **Access** tokens needed to call protected APIs. PKCE is Proof Key for Code Exchange and is designed to prevent several attacks and to be able to securely perform the OAuth exchange from public clients. PKCE is an IETF standard documented in RFC 7636. In addition, it returns **Refresh** tokens that provide long-term access to resources on behalf of users without requiring interaction with those users. This is the **recommended** approach.
 
 ![Single-page applications-auth](./media/scenarios/spa-app-auth.svg)