Not Acceptable! An appropriate representation of the requested resource could not be found on this server. This error was generated by Mod_Security

I was experiencing same issue with my WP site shared-hosted in HostMonster. I resolved simply by accessing to the server via SSH and added the following lines on the .htaccess file :

<IfModule mod_security.c>
  SecFilterEngine Off
  SecFilterScanPOST Off
</IfModule>

Apache has a mod_security tool that tries to block SQL injections by url. This rule is also blocking some real urls. The solution is:

• access WHM in your dedicated server
• search for mod_security tools
• check if it's blocking some urls
• click in the rule id
• click in deploy and Restart Apache

if you don't have access to WHM in your server. Pass this issue to your server administrator.

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This is the rule that was blocking my urls

SecRule REQUEST_HEADERS|XML:/*|!REQUEST_HEADERS:Referer "\b(\d+) ?= ?\1\b|\'\"[\'\"] ?= ?[\'\"]\2\b" \ "phase:2,capture,t:none,t:urlDecodeUni,t:htmlEntityDecode,t:replaceComments,t:compressWhiteSpace,t:lowercase,ctl:auditLogParts=+E,log,auditlog,msg:'SQL Injection Attack',id:'959901',tag:'WEB_ATTACK/SQL_INJECTION',logdata:'%{TX.0}',severity:'2'"

Do you have experience in setting up servers? Is this hosted by yourself or is it a shared hosting package?

The reason I ask is because this is a server-side (Apache) issue.

First, make sure your .htaccess file doesn't have any silly rules in it. The error arises because the server is denying access.

Second, make sure your file permissions are set up correctly. Generally speaking, you want directories to be 7/0/0 or 7/5/0 and files to be 6/0/0 or 6/4/0.

Read this for more details on Moodle security guidelines.

As for the profile picture issue, I'm not entirely sure what you're referring to so unfortunately I'm unable to answer that question. I doubt the two issues are related from the sounds of things.