Cal.com (repository calcom/cal.diy) in versions <= 4.7.15 is vulnerable to cross-site scripting (XSS) on the publicly accessible single booking view (e.g., /booking/<id>). Booking question (form field) labels are rendered via React's dangerouslySetInnerHTML without proper input sanitization or CSP, so an attacker who can create an event type with a malicious booking question label can inject arbitrary HTML/JavaScript that executes when a victim visits the booking view URL. Self-hosted instances with open registration are particularly at risk. The issue is fixed in version 4.7.16.
https://www.vulncheck.com/advisories/cal-com-through-cross-site-scripting-via-booking-questions
https://github.com/calcom/cal.diy/security/advisories/GHSA-vgj7-76cw-h6f8
https://github.com/calcom/cal.diy/commit/00689fda0a30b8f933c096f02c1fe092a4206def
Published: 2026-07-23
Updated: 2026-07-24
Base Score: 8.7
Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:C/A:P
Severity: High
Base Score: 8.9
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L
Severity: High
Base Score: 9.3
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L
Severity: Critical
EPSS: 0.00298