I've played with the wording a little:

```
This attack might sound a little academic, and far from a practical
problem. We may have proven that the MAC is insecure by our
definition, but the only tags the attacker can successfully forge are
for very limited modifications of real messages. Specifically, the
attacker can only forge tags for a message that consists of a message
we sent, followed by some binary junk, followed by something the
attacker chooses. However, it turns out that for many systems, this is
```