diff --git a/R/icci.R b/R/icci.R
index f22278a..618c50a 100644
--- a/R/icci.R
+++ b/R/icci.R
@@ -65,6 +65,11 @@
 #' @export
 icci <- function(object1, object2, conf.level=.95, ll1=llcont, ll2=llcont) {
 
+  ## Security validation for inputs
+  if (length(conf.level) != 1 || !is.numeric(conf.level) || is.na(conf.level) || conf.level <= 0 || conf.level >= 1) {
+    stop("Argument 'conf.level' must be a single numeric value between 0 and 1.", call. = FALSE)
+  }
+
   ## check objects, issue warnings/errors, get classes/calls
   obinfo <- check.obj(object1, object2)
   callA <- obinfo$callA; classA <- obinfo$classA
diff --git a/R/vuongtest.R b/R/vuongtest.R
index 2bdfbf6..f061505 100644
--- a/R/vuongtest.R
+++ b/R/vuongtest.R
@@ -98,6 +98,14 @@
 #' @export
 vuongtest <- function(object1, object2, nested=FALSE, adj="none", ll1=llcont, ll2=llcont, score1=NULL, score2=NULL, vc1=vcov, vc2=vcov) {
 
+  ## Security validation for inputs
+  if (length(nested) != 1 || !is.logical(nested) || is.na(nested)) {
+    stop("Argument 'nested' must be a single logical value (TRUE/FALSE).", call. = FALSE)
+  }
+  if (length(adj) != 1 || !is.character(adj) || is.na(adj) || !(adj %in% c("none", "aic", "bic"))) {
+    stop("Argument 'adj' must be a single character string ('none', 'aic', or 'bic').", call. = FALSE)
+  }
+
   ## check objects, issue warnings/errors, get classes/calls
   obinfo <- check.obj(object1, object2)
   callA <- obinfo$callA; classA <- obinfo$classA
diff --git a/tests/testthat/test_exported_input_validation.R b/tests/testthat/test_exported_input_validation.R
new file mode 100644
index 0000000..08fceb6
--- /dev/null
+++ b/tests/testthat/test_exported_input_validation.R
@@ -0,0 +1,34 @@
+expect_exported_boundary_error <- function(expr, message) {
+  err <- tryCatch(expr, error = identity)
+  expect_s3_class(err, "error")
+  expect_identical(conditionMessage(err), message)
+  expect_null(conditionCall(err))
+}
+
+test_that("vuongtest validates option arguments at the exported boundary", {
+  nested_message <- "Argument 'nested' must be a single logical value (TRUE/FALSE)."
+  for (value in list(logical(), NA, c(TRUE, FALSE), 1, "yes", NULL)) {
+    expect_exported_boundary_error(
+      vuongtest(NULL, NULL, nested = value),
+      nested_message
+    )
+  }
+
+  adj_message <- "Argument 'adj' must be a single character string ('none', 'aic', or 'bic')."
+  for (value in list(character(), NA_character_, c("none", "aic"), "AIC", "", "aic ", "other", 1, NULL)) {
+    expect_exported_boundary_error(
+      vuongtest(NULL, NULL, adj = value),
+      adj_message
+    )
+  }
+})
+
+test_that("icci validates confidence levels at the exported boundary", {
+  conf_message <- "Argument 'conf.level' must be a single numeric value between 0 and 1."
+  for (value in list(numeric(), NA_real_, NaN, Inf, -Inf, c(0.9, 0.95), 0, 1, -0.1, 1.1, "0.95", NULL)) {
+    expect_exported_boundary_error(
+      icci(NULL, NULL, conf.level = value),
+      conf_message
+    )
+  }
+})