This patch prevents a code execution vector involving terminal escape
sequences when rxvt-unicode is in "secure mode".

This change was spurred by the following conversation on the
oss-security mailing list:

Problem description and proof of concept:
http://seclists.org/oss-sec/2017/q2/190

Upstream response:
http://seclists.org/oss-sec/2017/q2/291

Patch copied from upstream source repository:
http://cvs.schmorp.de/rxvt-unicode/src/command.C?r1=1.582&r2=1.583

--- rxvt-unicode/src/command.C	2016/07/14 05:33:26	1.582
+++ rxvt-unicode/src/command.C	2017/05/18 02:43:18	1.583
@@ -2695,7 +2695,7 @@
         /* kidnapped escape sequence: Should be 8.3.48 */
       case C1_ESA:		/* ESC G */
         // used by original rxvt for rob nations own graphics mode
-        if (cmd_getc () == 'Q')
+        if (cmd_getc () == 'Q' && option (Opt_insecure))
           tt_printf ("\033G0\012");	/* query graphics - no graphics */
         break;
 
@@ -2914,7 +2914,7 @@
         break;
 
       case CSI_CUB:		/* 8.3.18: (1) CURSOR LEFT */
-      case CSI_HPB: 		/* 8.3.59: (1) CHARACTER POSITION BACKWARD */
+      case CSI_HPB:		/* 8.3.59: (1) CHARACTER POSITION BACKWARD */
 #ifdef ISO6429
         arg[0] = -arg[0];
 #else				/* emulate common DEC VTs */
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<div class='path'>path: <a href='/hydrilla-builder/log/?h=v1.1-beta1&amp;id=0009efd8588b462cfbbc6d69c1dcc1cf2230dd4a'>root</a>/<a href='/hydrilla-builder/log/doc?h=v1.1-beta1&amp;id=0009efd8588b462cfbbc6d69c1dcc1cf2230dd4a'>doc</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/hydrilla-builder/log/doc?h=v1.1-beta1&amp;id=0009efd8588b462cfbbc6d69c1dcc1cf2230dd4a&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-04-22 14:52:29 +0200'>2022-04-22</span></td><td><a href='/hydrilla-builder/commit/doc?h=v1.1-beta1&amp;id=6f745d21bf2005d1f86e65f3d5e0b3b496613326'>document --version option in the manpage</a></td><td>Wojtek Kosior</td></tr>
<tr><td><span title='2022-03-01 17:41:52 +0100'>2022-03-01</span></td><td><a href='/hydrilla-builder/commit/doc?h=v1.1-beta1&amp;id=363cbbb6a9fac49a377d8fa13ffede1483feabd5'>add Hydrilla builder manpage</a></td><td>Wojtek Kosior</td></tr>