add article about ssti

Author: xanhacks

content/docs/getting-started/vulnerability-reports.md

@@ -53,9 +53,10 @@ toc: true
 ## PHP
 
 - [Article - PHP filters chain: What is it and how to use it](https://www.synacktiv.com/en/publications/php-filters-chain-what-is-it-and-how-to-use-it.html)
-  - [Github - synacktiv/php_filter_chain_generator](https://github.com/synacktiv/php_filter_chain_generator)
+- [Github - synacktiv/php_filter_chain_generator](https://github.com/synacktiv/php_filter_chain_generator)
 - [Article - PHP filter chains: file read from error-based oracle](https://www.synacktiv.com/publications/php-filter-chains-file-read-from-error-based-oracle)
-  - [Github - synacktiv/php_filter_chains_oracle_exploit](https://github.com/synacktiv/php_filter_chains_oracle_exploit)
+- [Github - synacktiv/php_filter_chains_oracle_exploit](https://github.com/synacktiv/php_filter_chains_oracle_exploit)
+- [Article - SSTI on Twig + Symfony](https://heapcreate.com/posts/understanding_ssti/)
 
 ## Ruby