Cal.com (calcom/cal.diy) versions through 4.7.15 contain a stored cross-site scripting vulnerability. The single booking view (e.g., https://app.cal.com/booking/<id>) renders booking-question field labels via React's dangerouslySetInnerHTML without sanitizing or escaping user input. An attacker who can create an event type with a malicious booking-question label can inject arbitrary HTML/JavaScript that executes when a victim opens the crafted booking URL. The issue is fixed in v4.7.16.
https://www.vulncheck.com/advisories/cal-com-through-cross-site-scripting-via-booking-questions-2
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: 0.00291