<s>
Xpdf	B-Protocol
is	O
a	O
free	B-License
and	I-License
open-source	I-License
PDF	B-Language
viewer	I-Language
for	O
operating	B-General_Concept
systems	I-General_Concept
supported	O
by	O
the	O
Qt	B-Language
toolkit	I-Language
.	O
</s>
<s>
Versions	O
prior	O
to	O
4.00	O
were	O
written	O
for	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
and	O
Motif	B-Application
.	O
</s>
<s>
Xpdf	B-Protocol
runs	O
on	O
nearly	O
any	O
Unix-like	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
.	O
</s>
<s>
Binaries	O
are	O
also	O
available	O
for	O
Windows	B-Application
.	O
</s>
<s>
Xpdf	B-Protocol
can	O
decode	O
LZW	B-Algorithm
and	O
read	O
encrypted	O
PDFs	B-Application
.	O
</s>
<s>
The	O
official	O
version	O
obeys	O
the	O
DRM	O
restrictions	O
of	O
PDF	B-Application
files	I-Application
,	O
which	O
can	O
prevent	O
copying	O
,	O
printing	O
,	O
or	O
converting	O
some	O
PDF	B-Application
files	I-Application
.	O
</s>
<s>
There	O
are	O
patches	O
that	O
make	O
Xpdf	B-Protocol
ignore	O
these	O
DRM	O
restrictions	O
,	O
and	O
these	O
restrictions	O
are	O
patched	O
out	O
by	O
the	O
Debian	O
distribution	O
.	O
</s>
<s>
Xpdf	B-Protocol
includes	O
several	O
programs	O
that	O
do	O
n't	O
need	O
an	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
,	O
including	O
some	O
that	O
extract	O
images	O
from	O
PDF	B-Application
files	I-Application
or	O
convert	O
PDF	B-Application
to	O
PostScript	B-Language
or	O
text	O
.	O
</s>
<s>
These	O
programs	O
run	O
on	O
DOS	B-Device
,	O
Windows	B-Application
,	O
Linux	B-Application
and	O
Unix	B-Application
.	O
</s>
<s>
Xpdf	B-Protocol
is	O
also	O
used	O
as	O
a	O
back-end	O
for	O
other	O
PDF	B-Language
readers	I-Language
frontends	O
such	O
as	O
KPDF	O
and	O
GPDF	O
,	O
and	O
its	O
engine	O
,	O
without	O
the	O
X11	B-Operating_System
display	O
components	O
,	O
is	O
used	O
for	O
PDF	B-Language
viewers	I-Language
including	O
BePDF	B-Language
on	O
BeOS	B-Application
,	O
'	O
!	O
PDF	B-Application
 '	O
on	O
RISC	B-Operating_System
OS	I-Operating_System
,	O
on	O
PalmPDF	O
on	O
Palm	B-Operating_System
OS	I-Operating_System
and	O
on	O
Windows	B-Application
Mobile	O
.	O
</s>
<s>
Two	O
versions	O
exist	O
for	O
AmigaOS	B-Application
.	O
</s>
<s>
Xpdf	B-Protocol
needs	O
a	O
limited	O
version	O
of	O
an	O
X11	B-Operating_System
engine	O
called	O
Cygnix	O
on	O
the	O
host	O
system	O
.	O
</s>
<s>
AmigaOS	B-Application
4	I-Application
included	O
AmiPDF	O
,	O
a	O
PDF	B-Language
viewer	I-Language
based	O
on	O
3.01	O
version	O
of	O
the	O
Xpdf	B-Protocol
.	O
</s>
<s>
However	O
both	O
Apdf	O
and	O
AmiPDF	O
are	O
native	O
and	O
need	O
no	O
X11	B-Operating_System
.	O
</s>
<s>
The	O
associated	O
package	O
"	O
xpdf-utils	O
"	O
or	O
"	O
poppler-utils	O
"	O
contains	O
tools	O
such	O
as	O
pdftotext	B-Language
and	O
pdfimages	B-Language
.	O
</s>
<s>
A	O
vulnerability	O
in	O
the	O
Xpdf	B-Protocol
implementation	O
of	O
the	O
JBIG2	B-Algorithm
file	O
format	O
,	O
re-used	O
in	O
Apple	O
's	O
iOS	B-Application
phone	O
operating	O
software	O
,	O
was	O
used	O
by	O
the	O
Pegasus	B-Application
spyware	I-Application
to	O
implement	O
a	O
zero-click	O
attack	O
on	O
iPhones	B-Device
by	O
constructing	O
an	O
emulated	O
computer	B-General_Concept
architecture	I-General_Concept
inside	O
a	O
JBIG2	B-Algorithm
stream	O
.	O
</s>
<s>
Apple	O
fixed	O
this	O
"	O
FORCEDENTRY	B-Application
"	O
vulnerability	O
in	O
iOS	B-Application
14.8	O
in	O
September	O
2021	O
.	O
</s>
