It was possible to accept an invitation opened by a different Weblate user.
Users should avoid leaving Weblate sessions with an unattended opened invitation.
Thanks to Nahid0x for responsibly disclosing this vulnerability to Weblate.
5.15Exploitability
AV:LAC:HAT:PPR:LUI:PVulnerable System
VC:LVI:LVA:NSubsequent System
SC:NSI:NSA:N1.0/CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N