<s>
Object-Graph	O
Navigation	O
Language	O
(	O
OGNL	B-Language
)	O
is	O
an	O
open-source	O
Expression	O
Language	O
(	O
EL	O
)	O
for	O
Java	B-Language
,	O
which	O
,	O
while	O
using	O
simpler	O
expressions	O
than	O
the	O
full	O
range	O
of	O
those	O
supported	O
by	O
the	O
Java	B-Language
language	I-Language
,	O
allows	O
getting	O
and	O
setting	O
properties	O
(	O
through	O
defined	O
setProperty	O
and	O
getProperty	O
methods	O
,	O
found	O
in	O
JavaBeans	O
)	O
,	O
and	O
execution	O
of	O
methods	O
of	O
Java	B-Language
classes	O
.	O
</s>
<s>
It	O
is	O
aimed	O
to	O
be	O
used	O
in	O
Java	B-Language
EE	I-Language
applications	O
with	O
taglibs	O
as	O
expression	O
language	O
.	O
</s>
<s>
OGNL	B-Language
was	O
created	O
by	O
Luke	O
Blanshard	O
and	O
Drew	O
Davidson	O
of	O
OGNL	B-Language
Technology	O
.	O
</s>
<s>
OGNL	B-Language
development	O
was	O
continued	O
by	O
OpenSymphony	O
,	O
which	O
closed	O
in	O
2011	O
.	O
</s>
<s>
OGNL	B-Language
is	O
developed	O
now	O
as	O
a	O
part	O
of	O
the	O
Apache	B-Language
Commons	I-Language
.	O
</s>
<s>
OGNL	B-Language
began	O
as	O
a	O
way	O
to	O
map	O
associations	O
between	O
front-end	O
components	O
and	O
back-end	O
objects	O
using	O
property	O
names	O
.	O
</s>
<s>
Luke	O
Blanshard	O
then	O
reimplemented	O
KVCL	O
using	O
ANTLR	B-Application
and	O
started	O
using	O
the	O
name	O
OGNL	B-Language
.	O
</s>
<s>
The	O
technology	O
was	O
again	O
reimplemented	O
using	O
the	O
Java	B-Language
Compiler	I-Language
Compiler	I-Language
(	O
JavaCC	B-Language
)	O
.	O
</s>
<s>
OGNL	B-Language
uses	O
Java	B-Language
reflection	B-Language
and	O
introspection	B-Application
to	O
address	O
the	O
Object	B-Application
Graph	I-Application
of	O
the	O
runtime	O
application	O
.	O
</s>
<s>
This	O
allows	O
the	O
program	O
to	O
change	O
behavior	O
based	O
on	O
the	O
state	O
of	O
the	O
object	B-Application
graph	I-Application
instead	O
of	O
relying	O
on	O
compile	O
time	O
settings	O
.	O
</s>
<s>
It	O
also	O
allows	O
changes	O
to	O
the	O
object	B-Application
graph	I-Application
.	O
</s>
<s>
Due	O
to	O
its	O
ability	O
to	O
create	O
or	O
change	O
executable	O
code	O
,	O
OGNL	B-Language
is	O
capable	O
of	O
introducing	O
critical	O
security	O
flaws	O
to	O
any	O
framework	O
that	O
uses	O
it	O
.	O
</s>
<s>
Multiple	O
Apache	B-Language
Struts	I-Language
2	I-Language
versions	O
have	O
been	O
vulnerable	O
to	O
OGNL	B-Language
security	O
flaws	O
.	O
</s>
<s>
As	O
of	O
October	O
2017	O
,	O
the	O
recommended	O
version	O
of	O
Struts	B-Language
2	O
is	O
2.5.13	O
.	O
</s>
<s>
Users	O
are	O
urged	O
to	O
upgrade	O
to	O
the	O
latest	O
version	O
,	O
as	O
older	O
revisions	O
have	O
documented	O
security	O
vulnerabilities	O
—	O
for	O
example	O
,	O
Struts	B-Language
2	O
versions	O
2.3.5	O
through	O
2.3.31	O
,	O
and	O
2.5	O
through	O
2.5.10	O
,	O
allow	O
remote	O
attackers	O
to	O
execute	O
arbitrary	O
code	O
.	O
</s>
<s>
Atlassian	O
Confluence	O
has	O
repeatedly	O
been	O
affected	O
by	O
OGNL	B-Language
security	O
issues	O
that	O
allowed	O
arbitrary	O
remote	O
code	O
execution	O
,	O
and	O
required	O
all	O
users	O
to	O
update	O
.	O
</s>
