memos is a privacy-first, lightweight note-taking service. A CORS misconfiguration exists in memos 0.20.1 and earlier where an arbitrary origin is reflected with Access-Control-Allow-Credentials set to true. This may allow an attacking website to make a cross-origin request, allowing the attacker to read private information or make privileged changes to the system as the vulnerable user account. This vulnerability is fixed in 0.21.0.
The product uses a cross-domain policy file that includes domains that should not be trusted.
A cross-domain policy file (“crossdomain.xml” in Flash and “clientaccesspolicy.xml” in Silverlight) defines a list of domains from which a server is allowed to make cross-domain requests. When making a cross-domain request, the Flash or Silverlight client will first look for the policy file on the target server. If it is found, and the domain hosting the application is explicitly allowed to make requests, the request is made. Therefore, if a cross-domain policy file includes domains that should not be trusted, such as when using wildcards, then the application could be attacked by these untrusted domains. An overly permissive policy file allows many of the same attacks seen in Cross-Site Scripting (CWE-79). Once the user has executed a malicious Flash or Silverlight application, they are vulnerable to a variety of attacks. The attacker could transfer private information, such as cookies that may include session information, from the victim’s machine to the attacker. The attacker could send malicious requests to a web site on behalf of the victim, which could be especially dangerous to the site if the victim has administrator privileges to manage that site. In many cases, the attack can be launched without the victim even being aware of it.