In general, impact of this plugin is information retrieval and manipulation, arbitrary code execution.
More details: there exist multiple vulnerabilities in Enable Media Replace plugin for WordPress:
1. Users can perform SQL injection attacks against the plugin.
2. Users can upload arbitrary files (for the example, PHP files) to retrieve or change important information in the SQL database.
Update the plugin.
Also, you can deactivate this plugin for a while and look for other plugins that will help you with the media handling.
Found a vulnerability that puts your sites at risk?