DOMPurify VS Highlight.js

DOMPurify

I saw that some people were injecting alerts. If you haven't fixed it yet, consider using something like DOMPurify to sanitize the HTML input before posting it to the db.

You mean from this article "Sanitize HTML strings"? https://phuoc.ng/collection/html-dom/sanitize-html-strings/

Yeah, that article really shouldn't imply that sanitization is "that easy". It does at least mention https://github.com/cure53/DOMPurify at the end but it should LOUDLY argue against attempting to write this particular thing yourself and promote that exclusively in my opinion.

It is highly recommended to use an XSS Sanitizer like DOMPurify to sanitize HTML and prevent XSS attacks. For Next.js projects, which prominently feature server-side rendering, Isomorphic DOMPurify is especially valuable. It offers a seamless sanitization process across both server and client, ensuring consistent HTML sanitization in environments like Next.js where a native server-side DOM isn't present.

Note: We’ve used DOMPurify to sanitize the HTML in the above code block. You can install it in Node.js with npm install dompurify. Include it in your HTML with .

body, input.value property, or body are all different). If you need to insert untrusted input into raw HTML, use a well-tested sanitizer such as DOMPurify.

Setting a strong Content Security Policy without unsafe-inline or unsafe-eval in the script-src or default-src directives is an effective defense-in-depth) measure to prevent modern browsers from executing attacker code even if the attacker is able to insert </code> elements into the page.</p> <p><strong>3. HTTP API injection</strong></p> <p>RESTful APIs, GraphQL, and other HTTP-based APIs are ubiquitous. When a web application makes an API call to another service, injection vulnerabilities are possible when that request includes untrusted input.</p> <p>Consider a contrived example in which a web app integrates with a payments service that has a REST API endpoint for creating a subscription: <code>POST /subscriptions/{product_id}?price_usd=<price></code> where <code>price_usd</code> is optional, and a pre-configured price is used if omitted. If an attacker controls the value of <code>product_id</code> and passes a value of <code>desired_product_id?price_id=0</code>, the web app would end up making a request to <code>POST /subscriptions/desired_product_id?price_id=0</code>, which would allow the attacker to sign up for a free subscription.</p> <p>In JavaScript, the standard way to sanitize untrusted inputs in URL paths is <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURIComponent"><code>encodeURIComponent</code></a>, which replaces problematic characters such as <code>?</code> and <code>/</code> with safe percent-encoded sequences. When inserting untrusted input into URL query parameters, <a href="https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams/URLSearchParams"><code>new URLSearchParams(queryParams)</code></a> provides a convenient, safe interface for building a query string from a JavaScript object of key-value pairs.</p> <p><strong>4. Shell injection</strong></p> <p>Backend APIs sometimes need to execute external commands on the machine where they run. Consider an API that performs <a href="https://en.wikipedia.org/wiki/WHOIS">WHOIS</a> lookups for a requested domain by executing the <code>whois</code> command locally.</p> <p>Consider the following <strong>vulnerable</strong> Node.js code:</p> <pre><code>const whois = child_process.execSync(`whois ${whoisRequest.domain}`); </code></pre> <p>If an attacker can pass the domain <code>reddit.com && rm -rf /</code>, the backend will execute the command <code>whois reddit.com && rm -rf /</code>. The <a href="https://nodejs.org/api/child_process.html#child_processexecsynccommand-options"><code>child_process.execSync</code></a> function passes the command string to the shell (<code>/bin/sh</code> by default on Linux), which parses <code>&& rm -rf /</code> as a subsequent command to wipe the filesystem.</p> <p>To avoid this issue, <strong>never pass untrusted input to a shell</strong>. Instead, use an interface such as <a href="https://nodejs.org/api/child_process.html#child_processexecfilesyncfile-args-options"><code>child_process.execFileSync</code></a> that executes a specific binary (which shouldn't be a shell!) and passes arguments <em>as an array</em>:</p> <pre><code>const whois = child_process.execFileSync("whois", [whoisRequest.domain]); </code></pre> <p>Now, even if the user passes a domain <code>reddit.com && rm -rf /</code>, that entire string will be passed as the command-line argument to <code>whois</code>, which will exit with an error but will not cause any harmful side-effects. Perhaps an even better solution would be to use a library to perform WHOIS queries without needing to execute a separate command.</p> <p>Astute readers may point out that validating the domain against a regex would also likely prevent shell injection in this case. However, avoiding the possibility of shell injection by using a safe interface that keeps untrusted input away from a shell's command parser is a more robust solution that avoids shell injection in all cases.</p> <p><strong>5. Path traversal</strong></p> <p>Finally, a path traversal vulnerability arises when an untrusted input is inserted into a filesystem path, which can cause the wrong file to be read or even written. Consider a backend API that reads a file at the path <code>/teams/${team_id}/${report_name}.csv</code>. If an attacker controls the value of <code>report_name</code> but not <code>team_id</code>, they could pass a <code>report_name</code> of <code>../other_team_id/private.</code> This would cause the file <code>/teams/team_id/../other_team_id/private.csv</code> (resolved to <code>/teams/other_team_id/private.csv</code>) to be read, leaking data from a different team.</p> <p>To avoid path traversal vulnerabilities, <strong>never use untrusted input in file or directory names</strong>. It's safest always to control the names of files and directories, including IDs that you generate and control (e.g., UUIDs, KSUIDs, etc.). If the name of a file or directory absolutely <em>must</em> be derived from untrusted input, consider hashing it (e.g., using SHA-256) or at least encoding it into a format that doesn't include dots or slashes (e.g., <a href="https://datatracker.ietf.org/doc/html/rfc4648#section-5">URL-safe base64</a>).</p> <p>​</p> <p>Know of good Node.js libraries for avoiding injection vulnerabilities? Let folks know in the comments!</p> </div><!-- SC_ON -->

https://stackoverflow.com/questions/43584685/input-sanitization-in-reactjs https://www.npmjs.com/package/dompurify

If you're using an external view engine, or a javascript framework like react in addition to your ruby backend, you can rely on similar sanitization methods like the DOMPurify library.

You shouldn't roll your own for this. From what I've had to do web-wise, here's a few tools.

First, for the APIs, you need documentation: https://swagger.io/

From which you can generate JSON schemas and use those to validate in the browser and on the backend. https://www.npmjs.com/package/jsonschema

As well you should be writing a few more schemas for your application state and leverage the regex validation of your input components...

Speaking of which, you also need to sanitize out some potentially nasty input. https://www.npmjs.com/package/dompurify

Obviously this isn't everything and not perfect, but a lot of this tedium can be automated away if you have a few good examples of the happy path and some basic tests in place to prevent quick and dirty changes from poking holes in these layers.

> it was designed to resemble C#

I actually first heard of Vala just a few days ago when I was looking at a C#-related PR[1] for highlight.js:

> This fails the tests as the Vala default.txt is recognized now as C#. However, Vala is very close in syntax to C#, and the default.txt also seems to be valid C# so not sure what to do about this.

[1] https://github.com/highlightjs/highlight.js/pull/3906

About GitHub Source - https://github.com/highlightjs/highlight.js/issues/1224

Let's get started by installing the highlight js

Luckily, implementing syntax highlighting in our simple code editor is easy with the use of external libraries. There are several JavaScript libraries available, such as Prism and Highlight.js. For our editor, we'll use Prism since it's easy to use and supports a wide range of programming languages.

They do actually document the recommended path in their GitHub docs: https://github.com/highlightjs/highlight.js#GettingTheLibrar...

The templates grabs Markdown file data with XMLHttpRequest and converts it to HTML with https://showdownjs.com/ . Classless styles are done with https://picocss.com/ and code block syntax highlighting is done with https://highlightjs.org/ .

GitHub repo: https://github.com/dandalpiaz/markdown-pages

My search for a third-party syntax highlighter brought me to highlight.js. ctil converts text (.txt) and Markdown (.md) to generated HTML (.html) files, so I want the generated HTML files to support syntax highlighting. highlight.js can be used as HTML Tags by using a Content Delivery Network, CDN, so I was able to add highlight.js by adding the following lines to the generated HTML files:

The real magic is what happens once you generate the syntax trees; at that point, you can modify them with the existing plugins (or make you own, if you really want to). For instance, I use a plugin to add specific css classes to certain elements so they integrate better with the visual design of the website another to add code highlighting with highlight.js and some others for generating a js object from the frontmatter of a Markdown file and to add support for Github flavored Markdown. I could do a lot more with these, like add support for videos, embeds and more, but for now this is enough for a simple preview.

pre is for a block of preformatted text, so spaces are preserved, and the font can be monospaced. Another element is code for programming codes. Notice that code doesn't offer code highlighting; for this, use JavaScript + CSS code, like Highlight.js.