diff --git a/src/core/misc.c b/src/core/misc.c
index e589b8c5..4e9f4bbe 100644
--- a/src/core/misc.c
+++ b/src/core/misc.c
@@ -703,8 +703,11 @@ int expand_escape(const char **data)
 		*data += 2;
 		return strtol(digit, NULL, 16);
 	case 'c':
-                /* control character (\cA = ^A) */
-                (*data)++;
+		/* check for end of string */
+		if ((*data)[1] == '\0')
+			return 0;
+		/* control character (\cA = ^A) */
+		(*data)++;
 		return i_toupper(**data) - 64;
 	case '0': case '1': case '2': case '3':
 	case '4': case '5': case '6': case '7':
diff --git a/src/core/special-vars.c b/src/core/special-vars.c
index aaf8da8f..f254c200 100644
--- a/src/core/special-vars.c
+++ b/src/core/special-vars.c
@@ -384,6 +384,7 @@ char *parse_special(char **cmd, SERVER_REC *server, void *item,
 	}
 
 	nest_free = FALSE; nest_value = NULL;
+#if 0 /* this code is disabled due to security issues until it is fixed */
 	if (**cmd == '(' && (*cmd)[1] != '\0') {
 		/* subvariable */
 		int toplevel = nested_orig_cmd == NULL;
@@ -412,6 +413,9 @@ char *parse_special(char **cmd, SERVER_REC *server, void *item,
 
                 if (toplevel) nested_orig_cmd = NULL;
 	}
+#else
+	if (nested_orig_cmd) nested_orig_cmd = NULL;
+#endif
 
 	if (**cmd != '{')
 		brackets = FALSE;
diff --git a/src/fe-common/core/completion.c b/src/fe-common/core/completion.c
index e78fe7d5..fd452e5c 100644
--- a/src/fe-common/core/completion.c
+++ b/src/fe-common/core/completion.c
@@ -187,12 +187,18 @@ char *word_complete(WINDOW_REC *window, const char *line, int *pos, int erase, i
 			char *old;
 
 			old = linestart;
-			linestart = *linestart == '\0' ?
-				g_strdup(word) :
-				g_strdup_printf("%s%c%s",
-						/* do not accidentally duplicate the word separator */
-						line == wordstart - 1 ? "" : linestart,
-						old_wordstart[-1], word);
+			/* we want to move word into linestart */
+			if (*linestart == '\0') {
+				linestart = g_strdup(word);
+			} else {
+				GString *str = g_string_new(linestart);
+				if (old_wordstart[-1] != str->str[str->len - 1]) {
+					/* do not accidentally duplicate the word separator */
+					g_string_append_c(str, old_wordstart[-1]);
+				}
+				g_string_append(str, word);
+				linestart = g_string_free(str, FALSE);
+			}
 			g_free(old);
 
 			g_free(word);
diff --git a/src/irc/core/channel-events.c b/src/irc/core/channel-events.c
index b0bddab2..46bbd5fa 100644
--- a/src/irc/core/channel-events.c
+++ b/src/irc/core/channel-events.c
@@ -138,7 +138,13 @@ static void channel_change_topic(IRC_SERVER_REC *server, const char *channel,
 	g_free_not_null(chanrec->topic_by);
 	chanrec->topic_by = g_strdup(setby);
 
-	chanrec->topic_time = settime;
+	if (chanrec->topic_by == NULL) {
+		/* ensure invariant topic_time > 0 <=> topic_by != NULL.
+		   this could be triggered by a topic command without sender */
+		chanrec->topic_time = 0;
+	} else {
+		chanrec->topic_time = settime;
+	}
 
 	signal_emit("channel topic changed", 1, chanrec);
 }