Vitess is a database clustering system for horizontal scaling of MySQL. Users can either intentionally or inadvertently create a keyspace containing `/` characters such that from that point on, anyone who tries to view keyspaces from VTAdmin will receive an error. Trying to list all the keyspaces using `vtctldclient GetKeyspaces` will also return an error. Note that all other keyspaces can still be administered using the CLI (vtctldclient). This issue is fixed in version 16.0.1. As a workaround, delete the offending keyspace using a CLI client (vtctldclient).
https://github.com/vitessio/vitess/security/advisories/GHSA-735r-hv67-g38f
https://github.com/vitessio/vitess/commits/v0.16.1/
https://github.com/vitessio/vitess/commit/adf10196760ad0b3991a7aa7a8580a544e6ddf88