Form outside of wordpress gives wordpress 404 on submit

I have a wordpress site, and a subdirectory on that server which has been excluded from wordpress. This is the line I’m using in the .htaccess file to exclude that directory:

RewriteCond %{REQUEST_URI}  !(app) [NC]

I have a form inside that directory. Whenever one of the fields contains a URL, I get a wordpress 404 on submit. If the field does not contain a URL, it submits normally. How can I solve this issue?

EDIT:

Here’s what I’ve tried:

• Adding a prefix to the name of the form element
• Using a random string of characters as the form element name
• Encoding the value to base64 on form submission
• Adding an .htaccess file to the subdirectory with a RewriteEngine Off command
• Adding an “action” attribute to the form, both to itself and to another page, with relative and full URLs.

Here’s the full text of the wordpress .htaccess:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ - [L]
RewriteCond %{REQUEST_URI}  !(app) [NC]
RewriteRule ^other/(.*) /wp-includes/$1 [QSA,L]
RewriteRule ^file/(.*) /wp-content/uploads/$1 [QSA,L]
RewriteRule ^ext/(.*) /wp-content/plugins/$1 [QSA,L]
RewriteRule ^skin/main.css //index.php?style_wrapper=1 [QSA,L]
RewriteRule ^skin/(.*) /wp-content/themes/sirens/$1 [QSA,L]
RewriteRule ^ajax /wp-admin/admin-ajax.php [QSA,L]
RewriteRule ^wp-content/themes/sirens/screenshot.png|readme.html|license.txt|wp-content/debug.log|wp-includes/$ /nothing_404_404 [QSA,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress
<Files 403.shtml>
order allow,deny
allow from all
</Files>
## EXPIRES CACHING ##
<IfModule mod_expires.c>
ExpiresActive On
ExpiresByType image/jpg "access 1 year"
ExpiresByType image/jpeg "access 1 year"
ExpiresByType image/gif "access 1 year"
ExpiresByType image/png "access 1 year"
ExpiresByType text/css "access 1 month"
ExpiresByType text/html "access 1 month"
ExpiresByType application/pdf "access 1 month"
ExpiresByType text/x-javascript "access 1 month"
ExpiresByType application/x-shockwave-flash "access 1 month"
ExpiresByType image/x-icon "access 1 year"
ExpiresDefault "access 1 month"
</IfModule>
## EXPIRES CACHING ##
<ifModule mod_gzip.c>
mod_gzip_on Yes
mod_gzip_dechunk Yes
mod_gzip_item_include file .(html?|txt|css|js|php|pl)$
mod_gzip_item_include handler ^cgi-script$
mod_gzip_item_include mime ^text/.*
mod_gzip_item_include mime ^application/x-javascript.*
mod_gzip_item_exclude mime ^image/.*
mod_gzip_item_exclude rspheader ^Content-Encoding:.*gzip.*
AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/html
AddOutputFilterByType DEFLATE text/xml
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE application/xml
AddOutputFilterByType DEFLATE application/xhtml+xml
AddOutputFilterByType DEFLATE application/rss+xml
AddOutputFilterByType DEFLATE application/javascript
AddOutputFilterByType DEFLATE application/x-javascript
</ifModule>

Here’s the form:

<form enctype="application/x-www-form-urlencoded" class="form-horizontal" method="post">
   <textarea id = "orders" name = "orders"></textarea>
   <input type="submit" value="Place order" class=" btn btn-blue">
</form>

In every case, the result is the same – it works without a URL in the field, but goes to a wordpress 404 page when there is a URL in the field.

Example:

• Textarea contains “foo”. The form submits without issue.
• Textarea contains “http://foo.com“. The form goes to a 404.