Reflected cross-site scripting vulnerabilities arise when data is copied from a request and echoed into the application’s immediate response in an unsafe way. An attacker can use the vulnerability to construct a request which, if issued by another application user, will cause JavaScript code to execute within the user’s browser in the context of that user’s session with the application. The attacker-supplied code can perform a wide variety of actions, such as stealing the victim’s session token or login credentials, performing arbitrary actions on the victim on their behalf, and logging their keystrokes.
Source: https://thehackernews.com/2011/03/inboxcom-cross-site-scripting-xss.html