This is a simple plugin for adding a warning to posts when there are malicious urls present in the content of the post. For identifying malicious urls this plugin uses Google Safe Browsing API V4 . The warning appears as below
For getting this plugin to work , you need to obtain an API key to access the Google Safe Browsing API . You have to follow this guideline to get an API key. Other than the API key you need a Client ID and a Client Version. These details are used by google for logging purposes. You can find more about those two parameters from here. You can set those parameters by clicking settings in front of the plugin name in Admin Settings -> Plugins
You can find source for the plugin here . You can find more about installing this plugin here .
FYI : The API key in the above image is not a valid key 
Here is a simple demo how my plugin works,