The vSphere Web Client (FLEX/Flash) contains an SSRF (Server Side Request Forgery) vulnerability in the vSAN Web Client (vSAN UI) plug-in. A malicious actor with network access to port 443 on vCenter Server may exploit this issue by accessing a URL request outside of vCenter Server or accessing an internal service.
https://www.vmware.com/security/advisories/VMSA-2021-0027.html