XF 1.5 "Bad Request" when sending a PM

[borgqueenx]

At random times i get the error in chrome:
Bad Request
Your browser sent a request that this server could not understand.

Apache/2.2.15 (CentOS) Server at www.cupcakethunder.eu Port 80

When i try to send someone a PM. Website replies/new threads etc seem to work fine.
When i then try on mobile it works.

 

[borgqueenx]

EDIT: when sending a pm with only a few words it works, but a normal size pm with like 50 words does not work.

 

[Mike]

This would generally mean the request isn't even reaching XF. There may be more details in your web server error log. You may need to bring your host to help identify the trigger. It may be a false positive with a security tool.

 

[borgqueenx]

thanks for the info. It seemed to be because save mode was enabled.