Web applications hosted on the cloud are exposed to cyberattacks and can be compromised by HTTP requests that exploit vulnerabilities. Platform as a Service (PaaS) offerings often provide a backup service that allows restoring application state after a serious attack, but all valid state changes since the last backup are lost. We propose Rectify, a new approach to recover from intrusions on applications running in a PaaS. Rectify is a service designed to be deployed alongside the application in a PaaS container. It does not require modifications to the software and the recovery can be performed by a system administrator. Machine learning techniques are used to associate the requests received by the application to the statements issued to the database. Rectify was evaluated using three widely used web applications - Wordpress, LimeSurvey and MediaWiki - and the results show that the effects of malicious requests can be removed whilst preserving the valid application data.