<s>
Email	B-Protocol
injection	I-Protocol
is	O
a	O
security	O
vulnerability	O
that	O
can	O
occur	O
in	O
Internet	O
applications	B-Application
that	O
are	O
used	O
to	O
send	O
email	O
messages	O
.	O
</s>
<s>
It	O
is	O
the	O
email	O
equivalent	O
of	O
HTTP	B-Protocol
Header	I-Protocol
Injection	I-Protocol
.	O
</s>
<s>
Like	O
SQL	B-Language
injection	I-Language
attacks	I-Language
,	O
this	O
vulnerability	O
is	O
one	O
of	O
a	O
general	O
class	O
of	O
vulnerabilities	O
that	O
occur	O
when	O
one	O
programming	O
language	O
is	O
embedded	O
within	O
another	O
.	O
</s>
<s>
When	O
a	O
form	O
is	O
added	O
to	O
a	O
Web	O
page	O
that	O
submits	O
data	O
to	O
a	O
Web	O
application	O
,	O
a	O
malicious	O
user	O
may	O
exploit	O
the	O
MIME	B-Protocol
format	O
to	O
append	O
additional	O
information	O
to	O
the	O
message	O
being	O
sent	O
,	O
such	O
as	O
a	O
new	O
list	O
of	O
recipients	O
or	O
a	O
completely	O
different	O
message	O
body	O
.	O
</s>
<s>
Because	O
the	O
MIME	B-Protocol
format	O
uses	O
a	O
carriage	O
return	O
to	O
delimit	O
the	O
information	O
in	O
a	O
message	O
,	O
and	O
only	O
the	O
raw	O
message	O
determines	O
its	O
eventual	O
destination	O
,	O
adding	O
carriage	O
returns	O
to	O
submitted	O
form	O
data	O
can	O
allow	O
a	O
simple	O
guestbook	O
to	O
be	O
used	O
to	O
send	O
thousands	O
of	O
messages	O
at	O
once	O
.	O
</s>
<s>
However	O
,	O
this	O
vulnerability	O
is	O
not	O
limited	O
to	O
PHP	B-Application
;	O
it	O
can	O
potentially	O
affect	O
any	O
application	O
that	O
sends	O
email	O
messages	O
based	O
on	O
input	O
from	O
arbitrary	O
users	O
.	O
</s>
