Vitess is a database clustering system for horizontal scaling of MySQL. The /debug/querylogz and /debug/env pages for vtgate and vttablet do not properly escape user input. The result is that queries executed by Vitess can write HTML into the monitoring page at will. These pages are rendered using text/template instead of rendering with a proper HTML templating engine. This vulnerability is fixed in 21.0.1, 20.0.4, and 19.0.8.

Affected: Go: vitess.io/vitess

### Summary

The `/debug/querylogz` and `/debug/env` pages for `vtgate` and `vttablet` do not properly escape user input. The result is that queries executed by Vitess can write HTML into the monitoring page at will.

### Details

These pages are rendered using `text/template` instead of rendering with a proper HTML templating engine.

### PoC

Execute any query where part of it is HTML markup, for example as part of a string. To make it easier to observe you might want to make sure the query takes a few seconds to complete, giving you time to refresh the status page.

Example query that can trigger the issue:

```sql UPDATE users SET email = CONCAT("<img src=https://cataas.com/cat/says/oops>", users.idUser, "@xxx") WHERE email NOT LIKE '%xxx%' AND email != "demo@xxx.com" ```

Result:


### Impact

Anyone looking at the Vitess status page is affected. This would normally be owners / administrators of the Vitess cluster.

Anyone that can influence what text show up in queries can trigger it. This would normally be pretty much everybody interacting with a system that uses Vitess as a backend.

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