Never realized there are so many rules for divisibility. This post fits in this category:

Forming an alternating sum of blocks of three from right to left gives a multiple of 7

299,999 would be 999 - 299 = 700 which is divisible by 7. And if we simply swap grouped digits to 999,299, it is also divisible by 7 since 299 - 999 = -700.

And as for 13:

Form the alternating sum of blocks of three from right to left. The result must be divisible by 13

So we have 999 - 999 + 299 = 299.

You can continue with other rules so we can then take this

Add 4 times the last digit to the rest. The result must be divisible by 13.

So for 299 it’s 29 + 9 * 4 = 65 which divides by 13. Pretty cool.

Thanks for clarification and great that this is not included in project, but couldn’t someone change the server side code and somehow see more info that goes through?

I know there is that HTML check in https://searx.space/ to see if search interface code is not heavily modified, but on server side anything could go on.

If requests are encrypted in a way that searxng does not see contents then it probably is not trivial to do, but there always is a possibility something clever could be done.

Aren’t all search queries available to whoever hosts an instance? In my eyes this is much worse to privacy and a much bigger risk unless you really know who is behind your chosen instance. I would trust some a company a bit more with safeguarding this information so it does not leak to some random guy.