Add changelog for 1.5.3 release (#5227) (#5228)

Author: lafriks

CHANGELOG.md

@@ -4,6 +4,10 @@ This changelog goes through all the changes that have been made in each release
 without substantial changes to our git log; to see the highlights of what has
 been added to each release, please refer to the [blog](https://blog.gitea.io).
 
+## [1.5.3](https://github.com/go-gitea/gitea/releases/tag/v1.5.3) - 2018-10-31
+* SECURITY
+  * Fix remote command execution vulnerability in upstream library (#5177) (#5196)
+
 ## [1.5.2](https://github.com/go-gitea/gitea/releases/tag/v1.5.2) - 2018-10-09
 * SECURITY
   * Enforce token on api routes (#4840) (#4905)