File upload filter bypass leading to stored XSS in microweber/microweber


Reported on

Mar 11th 2022


A User can upload .[a-z]html file (e.g. ahtml, bhtml, chtml, ddhtml, AS LONG AS it ends with html) with XSS payload. Upon upload, a URL with malicious html can be accessed and javascript will be executed.

Proof of Concept (taking chtml as example)

Step (1) Login to the demo portal with admin creds at

Step (2) Add new > Page > Add file in picture

Step (3) Upload below file with content below and named as xss.chtml <div onmouseover="alert(document.domain)" style="position:fixed;left:0;top:0;width:9999px;height:9999px;"></div>

Step(4) Access the link in response and once you move the cursor, alert box will be prompted image image


If an attacker can control a script that is executed in the victim's browser, they might compromise that user, in this case, an admin, by stealing its cookies.

We are processing your report and will contact the microweber team within 24 hours. 2 years ago
James Yeung modified the report
2 years ago
James Yeung modified the report
2 years ago
Bozhidar Slaveykov validated this vulnerability 2 years ago
James Yeung has been awarded the disclosure bounty
The fix bounty is now up for grabs
Bozhidar Slaveykov marked this as fixed in 1.2.12 with commit 33eb4c 2 years ago
Bozhidar Slaveykov has been awarded the fix bounty
This vulnerability will not receive a CVE
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