If BPS is blocking something it is blocked 100% of the time – there is no middle ground – it is all or nothing – blocked or not blocked. If some links are working and others are not then this is being caused by something else. Intermittent problems typically indicate a cache problem. BPS Query string exploits code starts from: # BEGIN BPSQSE BPS QUERY STRING EXPLOITS and ends at: # END BPSQSE BPS QUERY STRING EXPLOITS. Do NOT comment out this one security filter: RewriteCond %{QUERY_STRING} (sp_executesql) [NC]
– this one security filter needs to be uncommented or your site will crash. A pound sign # is used to comment out .htaccess code.
Also 403 errors are a standard error. They are not exclusive to BPS.
I installed and tested the Max Magazine theme and created a link from facebook to the test site – it worked fine without a 403 error.