diff --git a/NEWS.md b/NEWS.md
index b1b1b5303..379a6c682 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -28,7 +28,9 @@
 
 * Order of arguments in `wb_add_conditional_formatting()` changed, because previously overlooked `dims` argument was added. [642](https://github.com/JanMarvin/openxlsx2/pull/642)
 
-* New argument `gradientFill` was added to `create_dxfs_style()`. [651](https://github.com/JanMarvin/openxlsx2/pull/6501
+* New argument `gradientFill` was added to `create_dxfs_style()`. [651](https://github.com/JanMarvin/openxlsx2/pull/651)
+
+* Special characters are now escaped in conditional formatting. Hence, previously manually escaped conditional formatting needs updates. [666](https://github.com/JanMarvin/openxlsx2/pull/666)
 
 
 ***************************************************************************
diff --git a/R/conditional_formatting.R b/R/conditional_formatting.R
index 9b0fbae54..3b1daaa85 100644
--- a/R/conditional_formatting.R
+++ b/R/conditional_formatting.R
@@ -240,9 +240,9 @@ cf_create_contains_text <- function(dxfId, sqref, values) {
     </cfRule>',
     # cfRule
     dxfId,
-    values,
+    replace_legal_chars(values),
     # formula
-    values,
+    replace_legal_chars(values),
     strsplit(sqref, split = ":")[[1]][1]
   )
 
@@ -259,9 +259,9 @@ cf_create_not_contains_text <- function(dxfId, sqref, values) {
     </cfRule>',
     # cfRule
     dxfId,
-    values,
+    replace_legal_chars(values),
     # formula
-    values,
+    replace_legal_chars(values),
     strsplit(sqref, split = ":")[[1]][1]
   )
 
@@ -278,11 +278,11 @@ cf_begins_with <- function(dxfId, sqref, values) {
     </cfRule>',
     # cfRule
     dxfId,
-    values,
+    replace_legal_chars(values),
     # formula
     strsplit(sqref, split = ":")[[1]][1],
-    values,
-    values
+    replace_legal_chars(values),
+    replace_legal_chars(values)
   )
 
   cf_rule
@@ -298,11 +298,11 @@ cf_ends_with <- function(dxfId, sqref, values) {
     </cfRule>',
     # cfRule
     dxfId,
-    values,
+    replace_legal_chars(values),
     # formula
     strsplit(sqref, split = ":")[[1]][1],
-    values,
-    values
+    replace_legal_chars(values),
+    replace_legal_chars(values)
   )
 
   cf_rule
diff --git a/tests/testthat/test-conditional_formatting.R b/tests/testthat/test-conditional_formatting.R
index 0667a69fd..7f98d1001 100644
--- a/tests/testthat/test-conditional_formatting.R
+++ b/tests/testthat/test-conditional_formatting.R
@@ -799,3 +799,72 @@ test_that("conditional formatting with gradientFill works", {
   )
 
 })
+
+test_that("escaping conditional formatting works", {
+
+  wb <- wb_workbook()$
+    add_worksheet()$
+    add_data(x = "A & B")$
+    add_conditional_formatting(
+      cols = 1,
+      rows = 1:10,
+      type = "containsText",
+      rule = "A & B"
+    )$
+    add_worksheet()$
+    add_data(x = "A == B")$
+    add_conditional_formatting(
+      cols = 1,
+      rows = 1:10,
+      type = "containsText",
+      rule = "A == B"
+    )$
+    add_worksheet()$
+    add_data(x = "A <> B")$
+    add_conditional_formatting(
+      cols = 1,
+      rows = 1:10,
+      type = "containsText",
+      rule = "A <> B"
+    )$
+    add_worksheet()$
+    add_data(x = "A != B")$
+    add_conditional_formatting(
+      cols = 1,
+      rows = 1:10,
+      type = "notContainsText",
+      rule = "A <> B"
+    )
+
+  exp <- c(`A1:A10` = "<cfRule type=\"containsText\" dxfId=\"0\" priority=\"1\" operator=\"containsText\" text=\"A &amp; B\"><formula>NOT(ISERROR(SEARCH(\"A &amp; B\", A1)))</formula></cfRule>")
+  got <- wb$worksheets[[1]]$conditionalFormatting
+  expect_equal(exp, got)
+
+  exp <- c(`A1:A10` = "<cfRule type=\"containsText\" dxfId=\"1\" priority=\"1\" operator=\"containsText\" text=\"A == B\"><formula>NOT(ISERROR(SEARCH(\"A == B\", A1)))</formula></cfRule>")
+  got <- wb$worksheets[[2]]$conditionalFormatting
+  expect_equal(exp, got)
+
+  exp <- c(`A1:A10` = "<cfRule type=\"containsText\" dxfId=\"2\" priority=\"1\" operator=\"containsText\" text=\"A &lt;&gt; B\"><formula>NOT(ISERROR(SEARCH(\"A &lt;&gt; B\", A1)))</formula></cfRule>")
+  got <- wb$worksheets[[3]]$conditionalFormatting
+  expect_equal(exp, got)
+
+  ## imports quietly
+  wb$
+    add_worksheet()$
+    add_data(x = "A <> B")$
+    add_conditional_formatting(
+      cols = 1,
+      rows = 1:10,
+      type = "beginsWith",
+      rule = "A <"
+    )$
+    add_worksheet()$
+    add_data(x = "A <> B")$
+    add_conditional_formatting(
+      cols = 1,
+      rows = 1:10,
+      type = "endsWith",
+      rule = "> B"
+    )
+
+})