@thinkcomp error 403 seems due to the number of chars in the request. I suppressed the last (platform) and it worked.
I just let plat, it worked, but platf failed.
I tested on Chrome, exact same behavior.
Is there a limit at about 100 chars on the forum backend, to avoid trojan horse in request or avoid too complex requests ?
Tested with a dummy search text of 103 chars
Thisisadummyreqjusttohavemorethan80charactersandseeiftheserversreplieswith403errorandmorecharstotestfor
In fact fails at about 102 chars. Removing the last char (r) it works.
Exactly the same on Chrome.
Also found that there are verifications on the payload: https://stackoverflow.com/questions/26506575/what-causes-a-403-error-when-the-url-payload-contains-request