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Security Fix for Cross-site Scripting (XSS) - huntr.dev #860

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https://huntr.dev/users/alromh87 has fixed the Cross-site Scripting (XSS) vulnerability 🔨. alromh87 has been awarded $25 for fixing the vulnerability through the huntr bug bounty program 💵. Think you could fix a vulnerability like this?

Get involved at https://huntr.dev/

Q | A
Version Affected | ALL
Bug Fix | YES
Original Pull Request | 418sec#2
Vulnerability README | https://github.com/418sec/huntr/blob/master/bounties/npm/editor.md/1/README.md

User Comments:

📊 Metadata *

Bounty URL: https://www.huntr.dev/bounties/1-npm-editor.md

⚙️ Description *

filterHTML function has been enhanced to properly handle self closing html tags

💻 Technical Description *

filterHTML uses regExp to filter selectively but previous version won't match properly self closing tags leading to improper filtering, regExp has been updated
When using the 'on*' filter attributes where being loaded to Jquery object causing onload property execution

🐛 Proof of Concept (PoC) *

Insert in editor a self clossing element with event to execute code

  1. Download editor.md
    git clone https://github.com/pandao/editor.md
  2. Go into directory
    cd editor.md
  3. Make the content available with any web server
    php -S localhost:8080
  4. open http://localhost:8080/examples/html-tags-decode.html
  5. Filter code execution by clicking on Filter style,script,iframe|onclick,title,onmouseover,onmouseout,style
    (No code should be executed with this Filter)
  6. Insert element with payload usig the editor (New line is important):
    <img src="https://picsum.photos/200" style="position:fixed;left:0;top:0;width:200px;height:200px;z-index:100" onmouseover="alert('img execution...')"/>
    sss
    ```
    
  7. Code will be executed when passing the mouse over the image

Captura de pantalla de 2020-09-10 17-06-44

🔥 Proof of Fix (PoF) *

After fix code execution is avoided as specified

Captura de pantalla de 2020-09-10 17-18-57

👍 User Acceptance Testing (UAT)

Editor works properly after fix:

#Refs:

#715
#764
#816
#709
#701
#700

alromh87 and others added 9 commits March 26, 2020 00:40
Disable script and on events by default to avoid XSS.

User can enable by setting allowScript|allowOn

Readme updated
Merging fix on-behalf of @alromh87 (034-js-editor-md).
fixes #pandao#612
fixes #pandao#662
fixes #pandao#697
fixes #pandao#700
fixes #pandao#701
fixes #pandao#709
fixes #pandao#715
fixes #pandao#764
fixes #pandao#816

### Probably:
fixes #pandao#307
fixes #pandao#560
fixes #pandao#612
fixes #pandao#662
fixes #pandao#697
fixes #pandao#700
fixes #pandao#701
fixes #pandao#709
fixes #pandao#715
fixes #pandao#764
fixes #pandao#816

fixes #pandao#307
fixes #pandao#560
Enhance filterHTML Regexp to handle self closing tags
@langren1353
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langren1353 commented Apr 28, 2022

似乎一定程度上解决了,但是并没有完全解决
问题行
var text = (typeof el[1] !== "undefined") ? $(el[1]).text() : "";
测试样例:

<a href="zhangsan">sdasda</a> <a href="console.log('aa')">dsdfs</a>

可能的渲染结果为
image

将 $(el[1]).text()变更为$4即可

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3 participants