In website operation, comment sections and message boards are important channels for interacting with users and collecting feedback.However, this area where users can freely fill in content is often an entry point for potential security risks, especially cross-site scripting (XSS) attacks.As website administrators, we must ensure that the content entered by users is safe and not exploited maliciously when displayed on the frontend.Anqi CMS, as a system focusing on providing a secure and efficient content management solution, provides us with powerful tools to meet such challenges.Today, let's delve deeply into a very practical filter in Anqi CMS——escapejsIt can help us safely handle text submitted by users that may contain malicious JavaScript code.
Understand the risk of cross-site scripting (XSS) attacks.
In simple terms, XSS attack refers to an attacker injecting malicious scripts into a web page, which are then executed on the user's browser when other users visit the page.This could lead to user information being stolen, website content being tampered with, or even users being redirected to malicious websites.For example, an attacker may write a JavaScript code snippet in the comments, for example<script>alert(document.cookie);</script>If the website does not perform appropriate security handling, this code may be executed in the browser of other users, thereby stealing the user's Session Cookie.Therefore, strictly filtering and escaping all user inputs is the foundation of website security.
The built-in security mechanism of the AnQi CMS template
The Anqi CMS template engine (similar to Django syntax based on Go language) took security into consideration from the beginning. By default, all accesses through{{变量}}The text output will be HTML entity encoded. This means that if a user enters in the comments<script>alert('XSS');</script>It is not parsed by the browser as executable JavaScript code on the page, but is displayed as is.<script>alert('XSS');</script>This is a very important security mechanism, which effectively prevents most XSS attacks based on HTML.
However, in certain special scenarios, for example, when we need to display rich text content submitted by users (which may contain valid HTML tags), we may use|safefilter.|safeTell the template engine that this content is safe and does not require escaping. But please note that only when weCompletely trustThis content can be used only if it comes from a source or has been strictly cleaned and filtered on the backend|safeOtherwise, it will open a hole for XSS attacks.
escapejsFilter: JavaScript Context Security Guardian
Then,escapejsWhen does the filter come into play? Its main function is to escape special characters in text at the JavaScript level, so that they can be safely embedded as part of a JavaScript string in the page.This means it will convert newline characters, quotes, slashes, and so on to\uXXXXThe form of thus, in order to prevent malicious code from the user input to break through the boundaries of JavaScript string, and then execute arbitrary JavaScript code.
In the AnQi CMS template,escapejsThe usage is very intuitive:{{ obj|escapejs }}For example, if we want to pass the user's submitted comment content as a parameter to a JavaScript function or dynamically fill it into a JavaScript variable, we should useescapejs.
Assuming we have a JavaScript function that needs to display the user's comment content:
<script>
function displayComment(commentText) {
alert(commentText);
}
</script>
If the user entered你好，世界！'); alert('XSS'); //such content, we use it directly{{ user_comment }}to output and pass it todisplayCommentfunction, it will lead to the followingalert('XSS');is executed. The correct way to useescapejs:
`html