Input Validation / URL Scheme List

Description

URL Scheme list is an Input Validation vulnerability (CWE-20) that occurs in mobile applications and iOS. It is caused when an application's URL scheme list is not properly validated, allowing a malicious user to execute arbitrary code on the application. This vulnerability can lead to malicious code being executed on the user's device, allowing the attacker to gain access to sensitive information or data stored on the application. It is important to note that the URL scheme list must be exhaustive and regularly updated in order to prevent this type of attack.

Risk

The risk of this vulnerability is high as it can lead to sensitive information being leaked or stolen, or a malicious user gaining access to the application. This vulnerability can be exploited in any mobile application that uses a URL Scheme list and is not properly validated. It is also important to note that this vulnerability can be exploited even if the application is not actively running.

Solution

The solution to this vulnerability is to properly validate the URL Scheme list. This means that all URLs must be checked against a whitelist in order to ensure that only legitimate URLs are allowed to be used on the application. Additionally, it is important to regularly update the URL Scheme list in order to prevent malicious code from being executed on the application.

Example

The following code is an example of a URL Scheme list validation. It checks each URL against a whitelist and only allows those URLs that are present in the whitelist.

URLs = ["youtube.com", "facebook.com", "twitter.com"]

for url in URLs:
    if url not in whitelist:
        print("URL not allowed")
    else:
        print("URL allowed")