Cross-site Scripting (XSS) - Reflected in gnuboard/gnuboard5


Reported on

Dec 8th 2021


The reflected XSS vulnerability occurs to a flaw in the clean_xss_tags() function called in memo.php of Gnuboard 5. This clean_xss_tags() is a Sanitizer that removes XSS-vulnerable tags and attributes. However, it can bypass Sanitizer by using a newline character. (%0A, %0D, ETC)

Proof of Concept

1. Open the
2. you can see that occur a xss after login


Through this vulnerability, an attacker is capable to execute malicious scripts.

We are processing your report and will contact the gnuboard/gnuboard5 team within 24 hours. 2 months ago
Pocas modified their report
2 months ago
We have contacted a member of the gnuboard/gnuboard5 team and are waiting to hear back 2 months ago
We have sent a follow up to the gnuboard/gnuboard5 team. We will try again in 7 days. 2 months ago
gnuboard validated this vulnerability a month ago
Pocas has been awarded the disclosure bounty
The fix bounty is now up for grabs
gnuboard confirmed that a fix has been merged on 2e8161 a month ago
The fix bounty has been dropped
Jamie Slome
a month ago


Just for reference, the researcher requested a CVE, and has been confirmed by the maintainer here.

Jamie Slome
a month ago


CVE published! 🎉