modules/security/classes/general.post_filter.php/post_filter.php in the Web Application Firewall in Bitrix24 through 20.0.950 allows XSS by placing %00 before the payload.
Source: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-13758
Reference (s):
- https://blog.deteact.com/bitrix-waf-bypass/