1 files changed, 8 insertions, 4 deletions

diff --git a/libbb/die_if_bad_username.c b/libbb/die_if_bad_username.c
index c1641d376..8b4deec29 100644
--- a/libbb/die_if_bad_username.c
+++ b/libbb/die_if_bad_username.c
@@ -18,16 +18,20 @@
 
 void FAST_FUNC die_if_bad_username(const char *name)
 {
-        goto skip; /* 1st char being dash isn't valid */
+        /* 1st char being dash or dot isn't valid: */
+        goto skip;
+        /* For example, name like ".." can make adduser
+         * chown "/home/.." recursively - NOT GOOD
+         */
+
         do {
-                if (*name == '-')
+                if (*name == '-' || *name == '.')
                         continue;
  skip:
                 if (isalnum(*name)
                  || *name == '_'
-                 || *name == '.'
                  || *name == '@'
-                 || (*name == '$' && !*(name + 1))
+                 || (*name == '$' && !name[1])
                 ) {
                         continue;
                 }