Change UserAgent with third-party applications

When developing one online store, there was a problem that goods are not added to the cart.
As a result of debugging, it turned out that CMS takes me for a search robot, and they can't buy anything :-)



Cause:
')
...
[HTTP_USER_AGENT] => Mozilla/5.0 (Windows; U; Windows NT 5.1; ru; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.5.30729) FirePHP/0.3
...


The CMS is worth a regular check that everyone with a PHP user agent / is marked as PHP

What to do and who is to blame?

FirePHP developer?
Perhaps you do not need to change my user agent - this is sacred.

CMS developers?
On the one hand, they are protected from robots, on the other hand, shops lose buyers-developers.
qip, skype, etc. also love to change user agent.

I think so:
The search engine robots have no. From here it is not possible to have your own basket ... and in general there is a noindex and nofollow + clan in the basket is usually implemented as a submit, and the search engines should not submit anything.

Therefore, to prohibit the purchase by user agent is wrong.
And the attacker always changes his user agent without any problems.

PS And how can users protect themselves from applications that change useragent?